Category Archives: Maintenance Topics

Fuel Tank Replacement

This article applies to replacement of  diesel fuel tanks aboard a boat fit with a diesel propulsion engine and a diesel generator.  This article DOES NOT apply to gasoline fuel systems, which carry different risks, and different handling and construction considerations.

There are several choices for dealing with diesel fuel tank leaks.  Most if not all Taiwan built boats have tanks made of “mild steel.”  Also called “black iron,” these tanks are well known to develop leaks at welds and often, on the tops of the tanks.  A common cause of tank top failure is rainwater which leaks through deck fill openings and lies on the top of the tank in the area of the fill tube.

Some tank leaks can be plugged with sealants and/or adhesives, and while that may save up-front costs, it undoubtedly delays the inevitable and impairs the resale value of the boat.  Sanctuary developed a leak that could not be accessed for simple, external remediation.  After careful review of my options, and in consideration of the age of the boat, I chose to physically replace my OEM tanks.  I did this replacement as two completely independent projects, the first being replacement of the STBD tank (2017) that was leaking and could not be used.  The second project was replacement of the PORT tank (2018) as “predictive maintenance.”  This article documents my approach to the tank replacement project.

The major steps of the project plan for replacement of a diesel fuel tank include:

  1. Assess the extent of personal involvement to be invested in this project, based on personal preference, personal skills and boat configuration.
  2. If professional help will be hired, define the scope of the work to be contracted.
  3. Settle on design of the replacement tank solution.
  4. Contract/hire professional assistance.
  5. Empty the tank to be replaced.
  6. Gain physical access to the tank to be replaced.
  7. Perform demolition and removal of OEM/old tank.
  8. Qualify and hire fabricator for new tank.
  9. Wait patiently for the fabricator to complete tank build.
  10. Receive and place new tanks.
  11. Restore disrupted fuel and vent plumbing
  12. Restore vessel infrastructure and any disrupted electrical wiring and plumbing.
  13. Fill and calibrate new tank.
  14. Celebrate completion!

Because I have the necessary skills and tools, I decided to handle many parts of the project work myself.  However, I also decided I would hire a mechanic to cut out the OEM tanks and install the replacement tanks.  Tasks I took on myself included gaining access to the tanks so the mechanic could come in and begin to cut.  The mechanic would manage removal and disposal of the old tank, transport the replacement tanks from the fabricator to the boat, prepare the install location, move the replacement tanks into place, mechanically secure the tanks in place, and re-plumb the tanks.  I would then take over to button-up the work once the new tanks were secured in place, and replace disrupted electrical wiring and fuel system plumbing.  This approach worked well for me, and saved many thousands of dollars of professional hourly-billing labor time.

Aboard Sanctuary, the OEM configuration consisted of two, one-piece tank units of 160 gallon capacity, each, located athwartships in the hull, in a “saddle tank” configuration.  The OEM tanks were placed into the hull before the deck was installed, so physical clearance limitations made it impossible to install a single replacement tank of the OEM dimensions. The OEM tanks were 48” long, with a baffle at the lengthwise midline. It would have been possible to reduce the height of the OEM tank by 3”, but physical placement of a 48”, one-piece tank would have required removal of the engine to gain the needed clearance. Since we live aboard, removal of the engine was a significant impediment. However, two 24” tanks could be fit without engine removal, so two side-by-side 24” tanks became the design point I adopted. This approach also provided equivalence with the midline baffle of the OEM tank.

Using Lotus FreeLance drawing software, I created an engineering drawing for my replacement design, as shown in Figure 1 for my STBD side project.

Fig 1

Figure 1: Design of Replacement Tankage

The complete drawing set for the OEM tank, STBD and PORT replacement units and fabrication notes is here: 20180506_Monk_Fuel_Tank.

Between the mechanic and myself, it was agreed that I would do the site preparation work to gain physical access to the tank. On the STBD side, that involved total removal of the DC electrical system and batteries, relocation of AC distribution wiring to the aft half of the boat, and removal of a non-structural bulkhead covered with soundproofing tiles. Gaining access to the PORT tank involved removal of the main fuel supply rail and primary filter plumbing and removal of the control unit and hydraulic pump for our hydraulic thruster system.  On  the STBD side, the house batteries needed to be removed from the boat, so I used the genset start battery to power the house water pump and the waste macerators for the duration of that project.  Because the OEM STBD tank had leaked fuel, it was already empty.  On the PORT side, I pumped fuel from the OEM PORT tank to the newly replaced STBD tank to empty the PORT tank.

I recommend that frequent photographs be taken at many points as any complex project proceeds. It’s amazing how these photos help at assembly/re-assembly time. Figure 2 is a picture of the wiring of Sanctuary’s main battery box. Figure 3 shows the DC distribution wiring before the start of the project.  This distribution wiring is located on the bulkhead that covers the OEM STBD fuel tank:

Fig 2

Figure 2: Battery Box 1.

Fig 3

Figure 3: DC Distribution Wiring at the Start of the Project

After removal of the DC distribution wiring and temporary relocation of aft-running AC wiring, the soundproofing and bulkhead could be removed. That was a destructive process. The OEM bulkhead was 5/16” plywood – well, since Sanctuary was built in Taiwan, probably 8mm plywood – but non-structural. Figure 4 shows the OEM tank with access gained. At that point, an angle grinder was used to cut out the OEM mild steel (black iron) tank. Careful examination reveals two structural angle iron retainers holding the OEM tank in place. These angle iron retainers were re-installed after the new tanks were placed. Figure 5 shows the hull space, frames exposed, after the OEM tank was cut out:

Fig 4

Figure 4: OEM tank exposed

Fig 5

Figure 5: Tank location showing support frames

The replacement tanks were fabricated of 1/8″ (0.125″ ) Grade 5062 Aluminum.  The work was done by a local SW Florida metals shop. The fabricator pressure tested and certified the tanks. The individual tanks are light enough that they could be handled by one man (a younger, stronger man than I, however). Figure 6 shows the tanks staged on the dock, and Figure 7 shows them in their installed location with the angle iron retainers in place:

Fig 6

Figure 6: New aluminum tanks

Fig 7

Figure 7: New tanks in place

Note the length of fuel hose that interconnects the two tanks at the bottom. That hose is continuously filled with diesel fuel. Use USCG Type A1 fuel hose for that application. USCG Type A2 fuel hose is appropriate for the tank fill hose. Type A2 hose is rated for fuel, but not for applications that are continuously immersed in fuel. Note also that both tanks need to have a vent. Consider the drawing in Figure 1: fuel enters the “A” tank via the fuel fill in the deck, but then fills the “B” tank from the bottom up. The “B” tank must be able to vent captive air or that tank cannot fill. Likewise, for fuel to leave the “B” tank as it is consumed, air must be able to enter the void above the fuel in order for the tank to empty. In our case, the two vents from the “A” and “B” tanks tee into a single vent, which is mounted to an overboard vent fitting in the hullside. Finally, the tanks, the deck fill fitting and the vent thruhull fitting should be electrically bonded to the vessel’s bonding system, if equipped, to dissipate static electricity and prevent galvanic corrosion.

Fuel plumbing also merits special mention. The fuel valves used in diesel fuel systems are commonly made of naval bronze, which is galvanically active in direct contact with aluminum. To minimize galvanic corrosion at the tank fittings, use a 300-series (316L) stainless steel nipple or bushing (adapter) to isolate the anodic and cathodic metals of the bronze valve and the aluminum tank fittings. Bond the tanks to the vessel’s bonding system, if equipped.

With the tanks installed and secured in place, the bulkhead and the vessel’s wiring can be reinstalled. Figure 8 shows the replacement bulkhead in place, with an inspection port that allows access to the interconnecting fuel hose and it’s hose clamps. The temporarily relocated overhead electrical wiring is still evident in this picture. Figure 9 shows the batteries and finished DC electrical distribution system in their restored position.

Fig 8

Figure 8: Bulkhead with inspection port

Fig 9

Figure 9: Electrical Systems re-installed

When filling the new tank for the first time, I put in 10 gallons of diesel fuel at a time, and marked the sight glass meniscus as a fuel level reference. I find this simple calibration of the tank capacity to be extremely helpful in judging my cruising options as I travel.

The loss of 3” in height resulted in a loss of about 25 gallons of total tank capacity. Each boat is different. Each tank replacement project is different. For what I’ve described above, I spent $1750 to have the STBD tanks fabricated, pressure tested and certified. Labor and miscellaneous materials – like the A1 and A2 fuel hose, hose clamps and new fuel valves – was $1800. I invested at least 30 hours of my personal DIY labor doing demo, site prep and re-install work, so for those who choose to contract this total project, consider what that would add in billable cost if performed by a paid professional.  There were efficiencies gained in doing the STBD tank.  The fabrication cost of the PORT replacement tanks was only $1570, and the professional labor component was $1260.

There is no question, this is a major project. With the work done, don’t forget to celebrate.

Polybutylene (PB) Plumbing in Drinking Water Systems

Cruising south in 2017, I became aware that my house water pump was cycling on and off at random intervals.   I proceeded to change our water pump head/valve assembly, but that repair action attempt left the symptom unaffected.  After a period of vigorous self-denial, I had no choice but to accept that I must have had a slow leak somewhere in the house potable water system.

Sanctuary is a 1988 Taiwan-built trawler.  Many boats built in the period were fit with polybutylene (PB) plumbing and PB plumbing fittings.  PB water line “pipes” are gray in color, somewhat flexible, and the fitting are gray plastic.  Our PB system was marketed under the trade name of “Qest.”  Aboard Sanctuary, our potable water plumbing is 3/8” diameter tubing, which means 3/8” ID (inside diameter) and 1/2” OD (outside diameter).  The system fittings are, therefore, either  3/8” by 1/2” MPT (Male Pipe Thread) or 3/8” by 1/2” FPT (Female Pipe Thread).

In the 70s through early 90s, PB systems were used in many building, RV and boat applications.  When it became clear that PB fittings failed as they aged, there was a Class Action lawsuit settlement called COX v. Shell Oil et al.  to compensate PB installation failures in installations between January 1, 1978 through July 31, 1995.  The defective PB fittings were discontinued and the product removed from the market.  Today, replacement Qest fittings of “better” materials are available as replacement parts from a variety of sources, including big box stores, ACE Hdwr and many Internet vendors.

My leak was in the cold water feed to our galley and aft cabin shower, in a predictably inaccessible location.   In my search for the leak, I furthermore identified two non-leaking fittings with visible cracks in the body of the compression nut.  The leakeI had planned to replace two nuts and have some spares.  I wound up using five of those six nuts as I worked on the system.



Anyone with PB plumbing aboard should check it at least once a year for these kinds of failure.

DO NOT OVER-TIGHTEN THESE NUTS; no more than one-quarter turn past hand tight.

Diesel Engine Maintenance

When we bought Sanctuary, I had no prior experience with diesel engines.  To get myself started, I attended a diesel engine orientation course in Annapolis called “Diesel Dork.”  That course ran two full days and included “hands on” a working diesel.  What I mostly got from that course was the personal confidence that diesel engine maintenance is the same as, or simpler than, maintaining a gasoline engine.  My conclusions were:

1. Routine diesel maintenance is not difficult but can be a bit messy.  There are simple precautions and techniques to minimize messes.
2. Diesel-powered fuel systems are orders-of-magnitude safer to handle than their gasoline-powered counterparts, because diesel fuel does not flash or ignite at Standard Temperature and Pressure (STP).
3. Diesel engines do not have an ignition system, so all that’s needed for an otherwise healthy diesel engine to run is clean fuel and clean air.
4.  DIY mechanics need to form an honest self-assessment of their personal mechanical skills, experience and self-confidence.  Of critical importance is a sense of when to stop and call a professional; i.e., “know when you’re getting in over your head.”
5.  As a DIY mechanic, learn all you can about your own engine(s); don’t worry about anything more.
6.  Anyone with beginner or higher mechanical skills and the inclination to do mechanical work will be able to perform routine diesel engine maintenance.
7.  Anyone with moderate or higher DIY mechanic skills and experience will be able to remove and replace fuel injectors, lift pumps and adjust valve clearances, as discussed below.
8.  Anyone with the tools needed to work on gasoline engines or lawn tractors won’t need to make a large tool investment to work on a diesel engine.
9.  A review of routine service tasks will help new diesel owners develop a list of spare parts and consumables that the boat should carry aboard.

Some background for owners of diesel-powered boats to consider and understand:

1. A “Disabled Boat” event
When cars quit running on the road, tows are relatively easy; especially so in the age of cellphones.  When boats quit running on the water, getting help is not nearly as easy.  Some skill with boat mechanicals is as important to boat operators as navigation and seamanship skills.  If a boat quits while under way, operators should expect to be “alone and on-your-own” for a significant time period. Particularly so if far from shore, in remote areas or during periods of inclement or severe weather. Rough seas, rain, and sensitive or seasick persons and pets aboard will greatly complicate the experience. Even well maintained boats can have mechanical failures, so towing insurance programs from BoatUS and SeaTow can be very valuable in the US.

2. Diesel Engine Technologies in 2016
There are currently two major “generations” of diesel engines commonly found in boats. The classic (older) generation has mechanical fly-weight fuel injection systems and the newer has “computer” controlled common-rail fuel injection systems. Electronic controls are how newer diesels comply with US Clean Air Standards (Diesel Emissions Reduction Act, 2005, and Diesel Emissions Reduction Act, 2010). Classic mechanical fly-weight governed injection pump engines generally can not meet DERA standards and are not sold “new” in the US.  But across the “fleet” of work boats and pleasure craft, mechanically injected engines still represent the vast majority of the install base.  Mechanically injected engines are still in wide use in most other parts of the world. Parts for mechanically injected engines are universally available across North America. These engines will be with us for many years to come.

Other than for starting, mechanically injected engines do not need DC electric power to run. Computer-controlled common-rail injected engines do need power to run. This difference has significant implications to the overall reliability and failure modes of diesel-powered systems. Decline or loss of power due to battery issues can and does impair the operation of, or stop, computer-controlled engines. Design of computer-controlled diesel engine electrical systems must consider alternatives to prevent loss of adequate DC power.

3. Diesel fuel
A boat that has 500 gallons in tankage capacity and is run 80 hours per year is probably going to have aging and old fuel in its tanks.  Within weeks after the refining process is complete, diesel fuel begins to slowly break down. “Asphaltenes” are a molecular distillation residue of crude oil refining.  Asphaltenes tend to “clump together” in solution. Over time, they form increasingly larger and larger “clumps.” After long periods of storage, these clumps get big enough to contribute to clogging fuel filters.

Environmental water (rain, snow-melt) gets into fuel tanks primarily through deck fill ports.  (“Condensation” in tanks is not nearly the problem that urban legend would suggest.) Deck fill “O” rings deteriorate and crack, boats stand unattended for long periods, ice and snow lays on decks and water gets into tanks.  Anaerobic algae – “bugs” that don’t need air and live at the interface of fuel floating on water in dark tanks – begin to grow in the tank.  That algae is black, and is often seen in clogged fuel filters.  Algae can be quite thick, almost like cream soup, and it can and will contribute to clogging fuel filters.

Water and other fuel contaminants tend to settle to the bottom of fuel tanks. Diesel fuel floats on water. When a boat gets into rough seas, algae and contaminants in tank bottoms get stirred up and become suspended in the fuel, with the result that filters clog up. Clogged filters may cause the engine to stumble and run rough, and it may even stall. Undetected water contamination can stall engines, cause a “disabled boat” event, damage injection pumps and injectors and cause damage to internal engine parts.

4. Fuel Polishing
“Fuel Polishing” is the process of filtering water and contaminants out of aging fuel stored in boat tanks. This is a service procedure done at the convenience of the boat owner. The process is intended to prevent fuel contamination problems. Polishing is best accomplished by professional fuel cleaning services that use equipment capable of producing high pressures to create artificial turbulence in tanks. The turbulence stirs up any contamination on the bottom of fuel tanks, and the polishing process in turn filters the stirred up fuel to remove suspended contaminants and water.

Polishing systems as installed on boats generally do not have the pressure or volume handling capacity to stir up contaminants that have settled to the bottom of tanks. However, they do circulate the liquid fuel through on-board filters, and will filter any suspended contaminants. The best filtering option is to filter the fuel while passing it from one tank to a second, known-clean tank. That method filters 100% of the liquid fuel in one pass. Some polishing systems remove fuel from a tank, pass it through a filter, and then return it to the same tank from which it came. This is called “back-mixing,” and requires multiple tank volume passes through filters to completely remove suspended contaminants. From one expert: “filtering one tank turnover will theoretically remove 63% of the contaminants.  Filtering two tank volume turnovers will remove 86% of contaminants. Filtering three tank volume turnovers will remove 95% of contaminants. Filtering four tank turnovers will remove 98% of contaminants.” And so it goes…

A running diesel engine does not burn all of the fuel passed from the injection pump to the injectors. More fuel volume is supplied by the injection pump than can “fit” through the nozzles of fuel injectors. Excess fuel is returned to the tank in a fuel return line. That process amounts to “back-mixing polishing,” because the returned fuel has been filtered by the boat’s normal fuel filtration system. Diesel engines from different manufacturer’s are different in the percentage of unused fuel that is returned to the tanks.

Aboard Sanctuary, we turn over the fuel in our tanks several times per year, not through a polishing system, but through ordinary use of the boat.   We carry 320 gallons of diesel fuel, and we consume 500 gallons in traveling between Baltimore and Charlotte Harbor.  We are “snow birds,” and make that trip twice per year.  As we progressed along the Great Loop cruise, we burned 2217.9 gallons, so 2217.9/320=6.9 turns of the fuel in our tanks.  Fresh fuel eliminates – certainly reduces – the chances of fuel-related troubles.

5. Personal Safety – Working on Boat Systems
REMOVE ALL JEWELRY BEFORE WORKING AROUND ANY MECHANICAL OR ELECTRICAL SYSTEMS.  NO WATCHES, NO WEDDING RINGS, NO NECK CHAINS; NO VANITY JEWELRY OF ANY KIND!!!  A gold chain or wedding ring snagged in an engine belt can easily remove a body part, and the victim would consider himself lucky if that’s all that happened. NEVER WORK ALONE. Even though an assistant may not be needed for the work-at-hand, always have someone else nearby who can stop engines, disconnect power and/or call for help in case something bad happens.

6. Personal Safety – Injuries and Raw Water
Be extremely careful when working around and in raw water. Methodically avoid cuts and scrapes of hands, arms, legs and feet. IF CUT, IMMEDIATELY WASH THE CUT WITH A CONCENTRATED BLEACH SOLUTION OR ANTIBIOTIC SOAP. MONITOR HEALING CAREFULLY, AND FOR WEEKS AFTER INJURY. Sea water – both salt water AND fresh water – is biologically active. Raw water can contain bacteria that can cause extremely serious infections in humans. If any sign of infection appears, particularly weeks after healing would seem to be complete, see a physician and mention that you have worked in a seawater environment and exposed open cuts to that sea water. DON’T MESS WITH THIS. AMPUTATIONS ARE NOT UNCOMMON TO TREAT INFECTIONS THAT INITIALLY WERE NOT CORRECTLY DIAGNOSED AND TREATED. For more information, see my article on Mycobacterium Marinum on this website, here:

7. DIY Maintenance
Diesel engine maintenance tasks can be arranged and sorted into “simple,” “complex” and “advanced” categories. I use “complex” to mean many steps, but not involving specialized background knowledge, awareness or tools. Maintenance intervals can be based on usage, age, wear or repair. Look to manufacturer maintenance manuals for details of service procedures. What follows is a basic overview, certain specific conditional implications and some contextual thoughts. The reader is responsible to have the knowledge and skills to perform the detailed work associated with these tasks.

When I wrote this post, I was thinking of a boat’s main propulsion engine.  Gensets don’t have transmissions, but many of the maintenance activities described here do apply equally to diesel genset engines.  Discussion of specific engine maintenance activities follows:

1.  [Simple; Usage/Age.] Change fuel filters when necessary.  Diesel fuel is usually filtered in two stages: “primary” and “secondary.”  At least daily, monitor fuel suction levels at the primary filters and at the same time, check for the presence of any water in the filter’s fuel bowl. The ability to see water in the filter’s fuel bowl is key to avoiding engine shutdown and possible engine damage.

Primary filters are the first-in-line as fuel flows from the fuel tank towards the engine.   Primary filters are generally located ahead of the fuel “lift pump” in the fuel line. The lift pump creates suction (vacuum) which pulls fuel from the tank and through the primary filters.  Primary filters are almost universally of the “water separator” type.  Be sure filter housing covers and cover gaskets are seated and air tight after being replaced.

Secondary filters are second-in-line.  Secondary filters are located between the lift pump and the fuel injection pump in the fuel line, and are generally mounted on the engine’s block.  Secondary filters are pressurized in operation.  Some secondary filters are on the high-pressure output side of the injection pump, and those are very highly pressurized.  Because of the pressurization, be sure to use secondary filters that are rated for, and compatible with, the engine on which they are installed.  If unsure, buy filters from the engine’s parts dealer. Some manufacturer warrantees require using their own branded filters.  Be sure the filter and gasket are aligned and tight after being replaced. If the filter has a water-separator drains cock, be sure that drain cock is also tightly closed.

When changing fuel filters – particularly the secondary fuel filter – air will have to be “purged” from the filter and fuel supply lines.  Purging fuel lines is a simple but very important procedure.  A diesel engine with air in the fuel lines may stumble and run rough, may run progressively worse as engine load is increased, or may not start/run at all.  Many diesels will tolerate a little air and self-purge after a primary fuel filter change.  Sanctuary’s Cummins engine does, but some will not.

2.  [Simple; Usage.] Diesel engines require huge volumes of combustion air.  The air filter needs to be clean.  Monitor the condition of, and change air filters, as needed.  Keep hands, clothing and rags well away from an exposed air intake port of a running diesel engine.  Air suction at the intake manifold will suck body parts and rags right in (and ruin your whole day in an instant).

3.  [Simple; Usage/Age.] Learn to change the engine’s lubricating oil and oil filter.  I always change the oil filter at every oil change.  The oil change process is identical to that of a gasoline engine.  Use ONLY oil formulated for use in diesel engines (API Service Class=Cx-y”), NOT the oils that are formulated for gasoline engines (Service Class=Sx-y).  The “C” is for “compression,” the “S” is for “spark.”  The engine manufacturer’s owners manual will have details on what oil viscosity to use, how much oil is needed with and without the filter, and how often oil should be changed.  Follow the manufacturer’s recommendations to the letter.  On older engines, it’s a good idea to slightly increase the frequency of oil changes. DO NOT OVERFILL THE CRANKCASE.  Recycle used engine oil.  Regardless of the exact amount of oil the manufacturer calls for, the unique “personality” and mounting angle of each diesel engine will affect the final working level of the oil on the dipstick.  If the engine loses 1/2 quart after an oil change, and then that loss stops, don’t worry about it.  That level is what that particular engine “wants to have,” and it is not an indication of a problem.

4. [Complex as a system; simple in pieces.] The function of the engine cooling system of all boats is critical to the operation, performance and service life of the engine. In the words of one diesel engine expert, “Most engines ‘go bang’ as the result of overheating due to a failure to maintain the cooling system.” Think, plan and act accordingly.

Boat cooling systems are quite complex, but individual maintenance tasks are generally within the skills of DIY mechanics, and can be performed one-at-a-time. Most diesel configurations in boats have two-stage cooling systems.  Inspect and maintain this critical system from end-to-end, from the raw water inlet thru-hull to the exhaust port of the boat, and into each and every cooled mechanical component along the end-to-end cooling circuit.

4a. [Simple; Age.] Periodically inspect and clean the raw water sea strainer. I do this monthly, more often in areas where sea grasses are common. The sea strainer admits engine cooling water through the hull. The strainer assembly has a basket that will catch and trap sea weed and other water borne debris. Learn to close the thru-hull valve, disassemble the sea strainer, clean the debris basket, and restore the system to operation.

4b. [Simple; Age.] Periodically change the antifreeze coolant.  We do that every couple of years, and generally, any time I have to open the fresh water side of the cooling system (infrequent), which re-starts the two-year clock.  The coolant within the engine is referred to as the “fresh water side.” The fresh water side of the cooling system is physically separated from the “raw water” (“sea water”) side.  The fresh water side of the system contains a solution of clean tap water and ethylene glycol coolant, exactly like that of a car’s gasoline engine.  Do not fill the fresh water side with either undiluted (“pure”) ethylene glycol or plain tap water.  Use the proportion of water and glycol that the engine manufacturer recommends.  This is a mandatory check item when decommissioning for winter layup in a cold climate.

Safety note: NEVER use antifreeze products designed for potable (drinking water) water systems in engine cooling systems.  Use ethylene glycol in engines.  NEVER use glycol antifreeze in potable water systems, either.  The glycol is poisonous to humans and animals.

4c. [Simple; Usage/Age.] Periodically change the raw water impeller.  The “raw water” side of the cooling system circulates sea water through a “heat exchanger,” analogous to the radiator of a car.  In a boat’s “raw water” cooling system, hot antifreeze coolant passes over a set of tubes inside the heat exchanger.  Sea water passes through these tubes, and excess heat is removed in the discharged sea water (wet exhaust).

The sea water needed for engine and transmission cooling is circulated by a pump mounted on the engine.  The pump contains a synthetic rubber (nitrile) impeller.  The time interval between impeller changes depends on 1) age of the impeller, and/or 2) cumulative hours of use and/or 3) sediment conditions of the raw water in the area where the boat is being used.  Sanctuary cruises mainly the US East and Gulf Coasts, and we accumulate between 500 and 800 hours per year.  I change our impeller every spring, based primarily on cumulative engine hours.  Grit and sediments in raw water may necessitate more frequent changes in some places.  Relatively few engine hours accumulated over multiple years time would also warrant an impeller change.

4d. [Simple; Age.] The main engine heat exchanger unit needs two kinds of periodic service, which happen at different service intervals.

First, change cooling system zincs quarterly. The heat exchanger usually contains one or more zinc anodes to protect it from galvanic corrosion. Zincs are fit in the sea water side of the heat exchanger. Servicing zincs will result in sea water draining from the heat exchanger, but will not result in antifreeze loss.  The raw water circuit is self-priming after reassembly. Simple start the engine and watch for raw water flow from the exhaust.

Second, clean the heat exchanger seasonally. The raw water side of the heat exchanger contains whatever local raw water exists where the boat is floating, whether river/lake fresh water, ocean salt water or a brackish dilution. Raw waters are biologically active with local sea critters (slime, barnacles, worms, etc); salt water is particularly active.  Seasonally, we clean the heat exchanger by circulating a biocide cleaner and chemical calcium de-scaler through the running system. Every 3 – 4 years, we remove the heat exchanger and take it to a radiator shop to have it chemically de-scaled.

4e. [Simple; Usage/Age.] Most diesel engine raw water cooling systems have in-line “transmission coolers.” In-line coolers are just another form of heat exchanger. A pump in the transmissions circulates transmission fluid around tubes in the cooler, and circulating raw water flowing through the tubes cools the transmission fluid to remove heat. Generally, no maintenance is required on the transmission side. However, it is wise to seasonally remove the input raw water hose and check for debris in the input end of the transmission cooler. Do this automatically if impeller vanes are missing when the raw water impeller is changed. Particularly if vanes break off raw water impellers, it’s highly likely they will get trapped at the first cooler they come to, usually the transmission cooler. Cooler tubes are too small to allow impeller pieces to pass, and the cooler will act like a debris “filter.” It is possible to compromise the effective cooling capacity of the entire cooling system if debris builds up in that cooler inlet. Handle the hoses at the transmission cooler gently to avoid deforming the cooler hose nipples.

Note: some OEM transmission coolers are not fit with zinc anodes. Galvanic corrosion can and will eat pinholes in the copper material from which heat exchangers are made. If a boat is kept in the water – especially salt water – change the cooler as a preventive maintenance action every 3 – 4 years, or every 2000 – 2500 hours. Some aftermarket companies make replacement coolers that do contain zinc anodes. I recommend using a cooler containing a zinc. If the boat is seasonally removed from the water, consult with a competent diesel mechanic for replacement interval recommendations. If this cooler develops an internal leak, sea water will enter the transmission and transmission fluid will be lost to the raw water. Nothing good can come from that scenario!

4f. I have excluded turbochargers, intercoolers and oil coolers in this discussion. Owners of engines fit with these devices must review the periodic maintenance recommended by the engine manufacturer.

5.  [Simple; Wear.] Know how to adjust belt tension, if belt tension is adjustable, and know how to change on-engine belts. Monitor on-engine drive belts (vee belts, serpentine belts) for wear and tension.

6. [Complex; One-time fitup.] All boats should have exhaust gas high temperature sensors to provide early warning of loss of raw water flow, such as might happen if a plastic bag were sucked into the raw water intake or if the raw water intake thruhull were inadvertantly left “closed.” Exhaust gas temperature sensors give warning of imminent system failure much earlier than engine coolant temperature sensors feeding engine gauges. They are easy to install, available in the aftermarket, and are an important safety adjunct to any boat with a wet exhaust. In a “wet exhaust,” environmental raw water is mixed with hot engine exhaust gasses to cool engine exhaust gasses. Diesel engine exhaust gas temperatures can reach 800ºF when the engine is under load. Many boats have rubber exhaust hoses and fiberglass waterlock “mufflers.” It is crucial that diesel exhaust gasses in wet exhaust systems be maintained at a low enough temperature that fiberglass mufflers and rubber exhaust hoses don’t “melt.” Cooling water leaks in the exhaust system of a boat can easily sink a boat.

7.  [Complex; repair.] Diesel engines are shut down by shutting off the flow if fuel to the engine.  The device that controls that function is called a “fuel solenoid,” which on my Cummins, is a part located on the side of my injection pump. The solenoid is an electrically-operated plunger that operates a fuel valve in the injection pump.  On mechanically injected diesels, there are two designs of these solenoids.  The “normally closed” design requires full-time DC power from the battery while the engine is running in order to hold the solenoid activated.  The “normally open” design only requires DC power from the battery to momentarily activate the solenoid, which shuts down the engine.  The “normally open” design has a pushbutton that is used to activate the solenoid to stop the engine.  Sanctuary’s Cummins diesel, OEM, has the “normally closed” design. It is controlled by a familiar “key-type” ignition switch on my gauge console.  Sanctuary’s fuel solenoid has failed in operation.  When it fails, the engine gets no fuel, and it shuts down or will not start. For diesel engines, I recommend the “normally open” solenoid design. On gasoline engines, the “normally closed” solenoid type is required by Federal Regulation (33 CFR 183.528).

With the “normally open” solenoid type, the engine can be shut down manually if the solenoid were to fail to operate.  On mechanically injected engines, there is a lever on the injection pump that closes the fuel shutoff valve manually.  Anyone with one of these engines MUST know how to do that.

Note: Intentionally closing off the fuel supply to a diesel engine allows the engine to be cranked without the engine starting.  This capability is useful in pre-oiling an engine that has not run in a long time, and may be useful in purging air out of the fuel system.  However, be methodically careful not to overheat the starter motor.  NEVER CRANK A STARTER MOTOR MORE THAN 15 – 30 seconds at a time, and allow several minutes between such operation for the motor to cool.

8. [Simple; Repair.] The Raw Water Pump of which the raw water impeller is a part needs periodic inspection, and periodic servicing. The raw water pump has a gear driven drive shaft. The drive gear is a component part of the central engine timing drive. Sanctuary’s pump and drive gear are built as a removable assembly consisting of the drive gear pressed onto the pump drive shaft, the engine mounting flange, a spacer and the pump housing body. The engine mounting flange contains a lip seal that eliminates lubricating oil leaks at the engine end of the shaft. The water pump housing contains a ceramic water seal that eliminates raw water leaks at the pump end of the shaft. The spacer mechanically separates  the mounting flange from the pump housing, and contains several “weep holes.” In operation, the vanes of the rotating impeller make continuous contact with the front cover plate, the internal cam, and the water chamber surfaces inside the pump. Not only does the impeller wear in use, but sediments suspended in the raw water abrade away the machined internal metal surfaces of the pump. Periodically, either the oil or water seals will begin to leak, and at that point, the pump will need servicing. Learn to remove and replace the pump. I do that approximately every two years, or whenever I note oil or water leakage around the weep holes at the shaft spacer. Rebuild kits are available for these pumps but I prefer to send them out for professional bench servicing.

9. [Simple; Repair.] The Fresh Water Pump is a centrifugal pump that circulates the antifreeze coolant solution through the engine itself, and through engine cooling system components. The belt-driven pump is mounted on the engine. Coolant loss and evidence of coolant leaks are the main symptoms leading to pump replacement. This pump is usually replaced as a unit with a new pump. Replace the antifreeze solution when replacing the fresh water pump.

10. [Complex; Repair.] Diesel engines have a thermostat, just as automobile engines do.  The thermostat sets the operating temperature of the engine coolant, and is very important to regulating the very high internal operating temperatures of internal engine parts, and therefore, proper engine operation and service life.  On our Cummins, it’s a complex task to get to it, but it’s not a technically advanced task. It would be wise to determine where the thermostat is located in the engine before there is an actual need-to-know. Follow the manufacturer’s recommendation for change interval.

11. [Simple; Repair.] The fuel lift pump pulls fuel from the fuel tank(s) by suction.  It in turn provides a low pressure, reliable fuel supply to the injection pump.  Dirty fuel filters place a lot of extra suction load on the lift pump.  Lift pumps can be of electric or mechanical diaphragm design.  Determine what type of lift pump is fit on the engine.  Like the thermostat, this is not a routine service item, but knowing how to change the lift pump can save a “disabled boat” scenario. When the pump is changed, it may be necessary to purge air from the fuel system.

12. [Complex; Usage.] Adjust valve clearances per the engine manufacturer’s service interval. The engine manual will have the specs for intake and exhaust valve clearances and adjustment interval.  My engine manual has a diagram of intake and exhaust valve locations.  Be obsessively careful to keep foreign materials out of the exposed valve train. Clean and vacuum any collected dirt and dust before removing the valve covers. Remove the valve cover(s), adjust the valves to specs, and replace the valve covers.  Aboard Sanctuary, the task takes less than one hour.  The only “special” tool is a set of flat feeler gauges; 0.010″ and 0.020″ are the sizes I need.  If it is necessary to replace valve cover gaskets as part of the job, obtain the replacement gasket kit ahead of time.

13. [Complex; Usage.] Diesel engine fuel injectors provide fuel to the cylinders.  As above, be obsessively careful to keep foreign materials, dust and grit out of the bore holes in the head. Injectors are pressure-activated valves.  Pulses of pressurized fuel arise at the injection pump. During the pulse, the injector valve opens to allow fuel into the cylinder. Flow flows into the cylinder while the pulse pressure is above the injector’s pre-set pressure (“pop-off”) value.  When the pulse pressure drops below the pop-off pre-set, the injector valve closes.  Not all of the fuel sent to the injector is actually injected into the cylinders.  Excess unused fuel returns to the tank via a common (shared) fuel return line.  That excess fuel return serves to cool the injectors.

Injectors need occasional maintenance; usually between 1500 and 3000 hours of operation.  Learn to pull the injectors to take them to a diesel shop for servicing.  Injector servicing requires highly specialized tools and equipment.  Important: when removing and replacing injectors from their bore in the cylinder head, the DIY-mechanic must be aware that there is a copper washer that seals the injector in its bore. These copper washers function as a gasket to prevent cylinder compression gasses from escaping the cylinder into the injector bore.  There is a second “copper” that seals the fuel return line at the injector discharge port.  Mechanics must be aware the copper at the base of the injector bore exists. When removing injectors, it is crucially important to get the old copper out of the bore hole.  If that copper is not removed, it will be impossible to reinstall the injector properly, which can lead to severe damage. Injector coppers usually come out with the injector body, but NOT ALWAYS. Procedures for removing the copper from the bore are in the maintenance manual for the engine.  Always replace the coppers with new when replacing injectors after servicing. When replacing injectors in their bore, verify that they are mechanically aligned with any guide in the bore. This aligns the nozzle in the head. BE CAREFUL NOT TO JAM THE INJECTOR ALIGNMENT SLOT/PIN IN THE BORE.

14. [Advanced; Usage.] There will come a time to have the injection pump serviced.  Servicing the pump is a repair shop activity.  Pump removal and replacement is an advanced DIY-mechanic task. This task does have important background knowledge associated with it.  Injection pumps have tapered shafts that mate with the engine’s timing gear.  Separating that taper from the timing gear requires a special tool; in the case of Sanctuary’s Cummins, an “H” puller.  Separating the pump from the timing gear is not hard, but I would class it as a complex and advanced skill.  There is a woodruff key that locates the pump shaft to the timing gear. Follow disassembly procedures provided by the engine manufacturer. In the case on my Cummins, THAT KEYWAY MUST BE LOCATED AT THE 12 O’CLOCK POSITION OF THE ROTATION OF THE PUMP SHAFT WHEN SEPARATING THE TAPER!  THIS PREVENTS HAVING THE WOODRUFF KEY FALL INTO THE ENGINE. Should that happen, it will be necessary to disassemble the entire front cover of the engine to retrieve it. Ugly!  Reinstalling the pump is easy.  Follow the manufacturer’s directions.

15. [Advanced; Repair.] Removing a cylinder head from an engine is a complex and advanced task. For those with the skills, it is certainly practical to do so on a boat in the water. This task does require a torque wrench and does involve associated technical background knowledge. The head can be pulled with the injectors in place. If the head is removed with the injectors in place, do not place the head assembly flat on any surface in a face-down orientation.  The injector nozzles extend very slightly below the plane of the head.  If the head is placed face-down, the injector’s fuel nozzles can get distorted or damaged.  That in turn will spoil the nozzle’s spray pattern.  It won’t become apparent that happened until the job is all re-assembled and the engine isn’t running well.

This is one task where it’s important to reassemble internal parts in the same place from which they came. Microscopic wear patterns in hardened metal surfaces matter here. Follow techniques to keep track of original parts locations. It is not necessary to pull a head to replace a broken valve spring, but compressed air and an air fitting for an injector seat would be needed. The process is the same as for a gasoline engine.

16. ALL “LOWER-HALF” ENGINE MAINTENANCE IS COMPLEX, AND MOSTLY ADVANCED STUFF. Other than perhaps replacing the front oil seal, I would not recommend doing lower-half maintenance with the boat in the water.

17. [Complex; Age.] Motor mounts can be changed with a boat in the water. This is a mechanically straight-forward task. However, it is necessary to separate the prop shaft at the transmission, and lift the weight of the engine off the mounts in order to replace them. Special safety considerations are necessary. Blocking and cribbing is needed, and any jacking tools need to be able to handle the weight of the engine. Be especially mindful that fingers, feet and extremities are always at risk. When done, it will be necessary to re-align the prop shaft to the engine. A feeler gauge will be needed for that task. DO NOT WORK WITHOUT HAVING SOMEONE NEARBY WHO CAN CALL FOR HELP IF NECESSARY.

18. [Simple; Usage/Age.] While not technically a part of the engine, change the transmission fluid at scheduled intervals. If the transmission has a reduction gear, change the lubricant in the reduction gear if that is a separate maintenance task.

Cleaning the A/C Raw Water Loop

Aboard Sanctuary, our normal summer and winter locations are mostly in brackish waters.  Local water temperatures rise into the mid-to-high 80s in the summer months.  Routine preventive maintenance is required to avoid the build-up of sea growth in the raw water circulation plumbing system.

The water that is circulated through heat pump plumbing systems is not biologically sterile.  It is drawn from the environmental water in which the boat is floating.  That water is referred to as environmental, or “raw” water.

All freon-based heat transfer systems work basically the same way.  In their cooling mode, heat is absorbed from the air in living spaces into the freon gas inside the sealed air conditioner system (R-12, R-22, R-134A).  The heat is transferred again from the internal freon gas through the metal walls of the unit’s heat exchanger into the circulating raw water.  The heat is discarded overboard, carried by the discharged raw water.  In their heating mode, heat is absorbed from the environmental “raw” water through the metal walls of the unit’s heat exchanger into the freon inside the sealed system.  That heat is transferred again within the unit into the air in the living spaces of the boat.

The maintenance issue in systems that circulate environmental “raw” water becomes the efficiency of heat transfer into and out of the circulating water.  The efficiency of the transfer of heat into and out of circulating raw water can be impaired by any accumulation of slime, algae and other biological “critters” attached to, and living on, the internal surfaces of raw water plumbing system components.  At its minimum, slime acts like an insulating blanket which impairs heat transfer.  In its worst case, it can build up to the point that it also occludes the lumen of the plumbing through which raw water circulates, acting like an insulating blanket AND decreasing water flow through the system.

To clean environmental biologicals from raw water plumbing fouled with sea growth, a couple of approaches can be tried, in order.  Raw water circulator pumps are high volume, low pressure pumps.  As a first step, if you have the capability to do so, close the intake thruhull, and swap a relatively higher pressure dockside fresh water hose to the raw water loop to the heat pump.  Do this just “downstream” of the circulator pump; i.e., at the discharge port of the pump.  The higher pressure of the dockside water may be sufficient to blow fouling material out of the raw water cooling loop system.  If this works, it’s less harsh than circulating chemical cleaning agents in the system.  If not, though, remove the dockside water hose and restore the circulator pump connection.   Re-open the cooling water thruhull, and prime the pump.  The next step is to place pool chlorine or bromine high test hypochlorite tablets (HTH) into the sea strainer basket.

Aboard Sanctuary, to control the growth of slime, algae and other sea life in the “raw” water loop of our two air conditioning heat pumps, we have used HTH pool “chlorine” tablets for several years.  The tablets are about the diameter of a Kennedy half-dollar, and about 5/16″ – 3/8″ thick.  We put as many of them as will fit into the sea strainer basket that supplies “raw” water to the air conditioners, and we then just run the units as normal.  These HTH pellets dissolve over 24 – 36 hours.  HTH works by releasing elemental oxygen into the raw water.  The elemental oxygen is a powerful oxidizing agent that kills and shrinks slime and other sea-life critters in the raw water loop. That allows the little corpses to slough off of internal plumbing surfaces and flow out of the system.  Physically clean surfaces allow better contact of raw water with the internal metal parts of the condenser/evaporator (cool/heat respectively) coils of the air conditioning unit, which increases heat transfer efficiency.

We perform this preventive maintenance procedure once or twice per season.

We do not use the HTH tablets in our genset or propulsion engine cooling circuits.  Doing so for the genset and the propulsion engine(s) would require them to be running to circulate the chemical.  With engine(s) not running, no raw water circulates and no cleaning would occur.  Also, the efficiency of heat transfer is not an equivalent issue with engines, and is not necessary, in engine cooling systems.

I hasten to add: “not necessary, in my opinion.”  There are significant design differences between air conditioning/heat pump raw water cooling systems and an engine’s raw water cooling system. In air conditioning systems, water flow is constant over a relatively small heat transfer surface area. Furthermore, in the first few minutes of operation, the temperature differential normalizes to a very steady state. Contact efficiency is very important to heat transfer. In engine cooling systems, flow is variable (with engine speeds) over a relatively high surface area. In engine systems, the amount of heat shed in the raw water cooling circuit varies widely, and the proportionate temperature differential is much higher. In engine cooling systems with high temperature differentials, the importance of contact efficiency is lessened. By and large, the capacity of engine cooling systems is significantly over-sized with respect to their nominal operating requirements. That large capacity accommodates extremes that may be encountered in severe operation.  Again, there is no analog to those severe operating conditions in air conditioning system design. So, the two systems are very different.

One common misconception is that calcium deposits will foul air conditioning and engine cooling systems. That is largely an “old wives tale,” often implied and promoted by product advertising. Yes, there are minerals in solution in sea water. Yes, those minerals can and do coat internal hose and metal lumen channels of raw water loops. But except under the most extreme situations, mineral deposits do not account for significant fouling of marine cooling systems. If they did, salt water would be a severe and ever-present disaster. Slime, algae, sea worms and barnacles – living sea creatures – are the problem. These critters grow quickly in warm sea water, foul plumbing lumens and impair heat transfer. It just so happens that de-mineralizing agents – RydLyme®, Lime-A-Way®, muriatic acid, hydrochloric acid – will also clean out slime, worms and dissolve the shells of barnacles and other sea critters. But, these agents are caustic in varying degrees to the internal metals of raw water-carrying loops, caustic to use safely, caustic to dispose of properly and safely, and generally “overkill” on a “fitness-for-purpose” scale. Free elemental oxygen, like that released by HTH, will kill biologicals without adversely affecting hoses, tubing, copper/nickel metals, etc. and they are generally safer for people to use and dispose of safely.

It is my opinion that HTH is the best first-use agent, and I suggest it as the primary, routine course of preventive maintenance. Reserve the caustic stuff for the less common, more intense and serious, corrective-action situations.

Early Monk36 Hydraulic Steering Systems

Although this post is specific to the classic Monk 36 trawler, the system description may be helpful to owners of boats of other manufacturers and other hull designs.

Sanctuary is fit with two Capilano (now Teleflex) model 250V helm pumps. Hydraulic systems based on these pumps were very common in the mid-80s to early-90s. They are a generation older than the model 1250V, which succeeded the 250V design in the early-90s. These systems are filled with hydraulic fluid.  When properly purged, there is no air in the closed hydraulic system. The 250V system is not pressurized.  In systems containing multiple helm or autopilot pumps at different vertical elevations, fluid is added from the pump at the highest elevation in the system. The highest pump in the system has an air space that functions as an expansion reservoir.  The expansion reservoir is vented to the atmosphere.  The overall system is maintained at its full level by gravity.

Hydraulic systems containing Capilano 250V pumps also contain a Model 50 Uniflow valve. The Uniflow valve converts the cylinder from an “unbalanced” design to a “balanced” design, and provides a return path for the flow of hydraulic fluid.

The Capilano 250V helm pumps have built-in pressure relief valves that vent hydraulic pressure when the mechanical limit-of-travel of the cylinder is reached. The mechanical limit-of-travel is referred to as its “stop.” When the steering wheel is turned fully “hard-to-port” or fully “hard-to-stbd,” at the point that the “stop” is reached, the check valve opens. At that point, the helmsman will feel only a very slight increase in back pressure. The wheel (pump’s shaft) will continue to turn indefinitely. However, the pump’s internal pressure relief valve opens to protect the pump and hydraulic system from any hydraulic over-pressure damage or ill effect.

On the model 250V pump, there is a knob beneath the pump’s shaft that adjusts the number of turns from stop-to-stop. To the helmsman, this can be thought of as a helm sensitivity adjustment. The knob adjusts a wobble plate internal to the pump. The wobble plate changes the fluid displacement volume of the pump. The hydraulic fluid displaced by the pump ranges from 1.7 in3 to 3.4 in3. The least number of stop-to-stop turns is around 4 full wheel revolutions, and the greatest number of stop-to-stop turns is around 7-3/4 wheel revolutions. A low number of stop-to-stop turns requires more steering effort on the part of the helmsman but also results in greater responsiveness to steering adjustments. Generally, this adjustment is made to suit the personal preference of the individual helmsman.
To manually “center” the rudder, the helmsman will have to learn to “feel” the point at which the internal 250V pressure relief valves release. When that point is reached in either direction, stop turning the wheel. While counting the number of turns, turn the wheel the other way until the check valve releases. Finally, turn the wheel back 1/2 the total number of turns, and the rudder will be centered. Over the course of the day, steering wheel indexing may change, but that is never a problem in operation.

Hydraulic fluid does not evaporate, nor is it consumed in use. Loss of hydraulic fluid is always related to a leak in the system. The most common hydraulic fluid leaks occur at the shaft seal of the 250V pump shaft or at the seals of the ram piston shaft. Less frequently, leaks can occur at hydraulic fittings anywhere in the system. If the level of the fluid in the pump reservoir gets low enough, air will be introduced into the sealed hydraulic systems and become entrapped in the system. Air in the system will generally cause the helm pump to “chatter” as air bubbles pass through it. The overall capacity of Sanctuary’s hydraulic system is 3-1/2 quarts of hydraulic fluid.

A temporary “fix” for a low fluid condition can be achieved by simply replacing the lost volume of fluid; i.e., “topping off” the reservoir. The definitive fix, however, is to find and correct the source of the leak. Hydraulic fluid is added to a level of 1″ below the fill ring of the highest elevation pump in the system. Manufacturer specs allow the use of Dexron III automotive transmission fluid on these steering systems, but I personally prefer to use Teleflex hydraulic fluid as sold in most chandleries sell. Follow manufacturer procedures for bleeding air from the hydraulic system. For Monk owners, I have posted those procedures here:

Refurbishing Leaking Windows

When we bought Sanctuary, we inherited several window leaks.  Yes, they were known, but undisclosed, by the seller, not found or tell-tales not recognized and understood by the surveyor, and so, they became ours to discover.  We were the 4th owners of the boat!  The first three owners – over 16 years – had all tolerated these leaks.  We were amazed.  For us, a leak in the non-opening stern window in the aft cabin was at the absolute top of our “must fix” list.  That particular leak, you see, was above the pillow on the Admiral’s side of the bed!  I pulled that window and took it to a glazier to have the glass re-set.  He told us that problem had been there since the original fabrication of the frame.  One glass-to-frame interface still had cosmoline on it, which was the reason for that leak.

Our 1988 Monk windows are set in aluminum frames.  Both the fixed and sliding glass panes are of common tinted safety glass as is available from any glazier.  The frame assemblies are, in turn, set in the fiberglass house/trunk rough openings.  A made-for-purpose structural sealant material is used by glaziers to “glue” glass panes into the metal window frame.  Rated for industrial applications and able to withstand hurricane force wind loads, our glazier recommended Dow Corning 995.  It’s a black “goo” that comes in a tube that fits into a standard caulk gun.  When 995 cures, it does not become hard and brittle; rather, it retains the look and feel of vulcanized rubber.  This allows it to move with the movement of a boat in a seaway.  I also used this same material to seat and seal the window frame assemblies into the fiberglass rough openings in the house and cabin trunk.  Buy it from Internet sources or from a glazier (glass shop).

To remove and reinstall the exterior wood trim, metal window frame assemblies from fiberglass rough openings, and refurbish the insulation weatherstripping, only simple tools are needed.  Tool items can be found at big box home centers or good hardware stores.  Weatherstripping will come from glaziers.  Sealant will come from Internet sources or glaziers:

  • a couple of miniature flat “pry bars.”  These are 6″ or so in overall length, shaped like the letter “L;” i.e., the size used to remove small finishing nails and staples from wooden screen door frames or carpet retainer strips.
  • a couple of 1″ and 2″ putty knives,
  • correctly sized weatherstripping,
  • battery powered drill with a household selection of drill bits,
  • a Dremel tool with a 1/8″ round burr,
  • fiberglass putty,
  • a standard caulk gun,
  • #2 Phillips screw driver,
  • one tube per small window, two tubes per large window: Dow Corning 995 sealant, and
  • a couple of 24″ bar clamps that can be used to pry apart/separate as well as squeeze.

If there is teak wood trim around the windows, the first step is to remove that exterior decorative trim.  Drill out the cosmetic bungs to expose the underlying stainless steel (ss) trim retaining screws, and then remove them.  Don’t be surprised if the fiberglass for some of the wood screw holes doesn’t grip the screw threads, because they were probably stripped when the screws were originally set with a power screwdriver.  That is probably what lead to the sealant failure and subsequent leaks in the first place.

Sanctuary’s windows do not have exterior Teak trim.  On late 80s Monks with aluminum window frames, there are decorative rubber trim molds that fit in a channel in the frame.  The trim hides the heads of SS frame retaining screws.  Between the window frame and the fiberglass, there is a sealant. That sealant is intended to remain weather tight, but if it fails, there will be interior rain water stains and leakage.  Finally, there are is weatherstripping insulation that keeps air from entering around the sliding surfaces of the movable window glass panes.  The 1980s vintage of that insulation is susceptible to age-related UV deterioration.

The metal window frame will be bonded into a rough opening in the fiberglass with a sealant.  It will not just fall out of the fiberglass opening into your hands.  Remove any and all frame retaining screws.  Using putty knives, break the old seal by gently but firmly jamming the blades between the frame and the fiberglass.   Then, work them gently but firmly apart from each other to continue to separate the sealant bond from the fiberglass.   When you’ve got 5″ or 6″ of broken sealant, pry slowly and firmly outwards with the putty knife blades to “encourage” the frame to lift away from the fiberglass of the house.  Once a small but sufficient gap has been attained, slip the short leg of the mini pry bars into that small gap.  Pry with just enough effort to ease the frame away from the fiberglass.  Be careful to exert just enough force to extract the frame, but not so much that the underlying fiberglass cracks or that the frame deforms.  To distribute the prying force on the underlying fiberglass, you can slip a putty knife blade under the fulcrum point of the pry bar.  Once the frame starts to come away, it gets easier and easier to break the sealant until the window assembly will come finally out of the fiberglass opening.  The window glass should be safety glass, and the window assembly will weigh 20# – 25#, so be prepared for the ungainly weight and bulk of that unit when it does come free.

At this point, you have another decision to make.  If you’re going to refresh the weatherstripping in the interior window channels, this is the time to do it.

To get access to the channels that hold and retain the weatherstripping, it will be necessary remove the fixed and sliding glass panels from the frame.  To remove the sliding glass panel, the frame must be slightly spread apart.  On Taiwan-vintage Monk windows, there is a flat metal bar across the full length of the interior bottom of the window frame.  The bar acts as a water dam to create a small reservoir that collects rain water and prevents it from spilling into the interior space.  To spread the frame enough to remove the sliding glass pane from the frame, you will first have to remove that flat bar.  The screws that retain the bar are very small and short.  They are Phillips head machine screws, 6mm – 8mm in length, with fine metric threads.  Use extreme care not to damage the Phillips head seats of those screws!  They can be hard to find. The bar will also be set in a fine film of window sealant gasket material.  Very gently, use the putty knife to separate the bar from the frame.  Do not bend or deform that bar, as doing so will make it virtually impossible to re-install and re-seal without leaks.

Once the bar is removed, use reverse acting bar clamps to gently spread (push) the top and bottom of the frame parts slightly apart.  Spreading the top and bottom very slightly will allow you to remove sliding glass pane from the frame.  Removing the sliding glass panel will give you the clearance you need to break the old seal of the fixed piece of glass, and get it out of the frame.  Finally, you will have access to the channels that retain the weatherstripping.

The appropriate weatherstripping can be difficult to locate.  There are many, many sizes and designs.  I was ultimately successful by going to multiple glaziers in the Sarasota metro area (happened to be where we were at that time) with samples of what I needed.  Storm windows are no longer made with that vintage of weatherstripping, but there are millions of installed units that periodically need repairing, so the stuff is available.  Be persistent.  The weatherstripping comes in rolls, and you should be able to buy it by the foot.  You’ll need 100′ or more to do all your windows.  From the many available sizes of weatherstripping, you’ll need two sizes for your windows. There’s a narrower size for the channels (approx 5/16″), and a wider size (approx 7/16″) that seals the sliding glass pane to the fixed glass pane.  DO NOT TRUST MY MEMORY; TAKE SAMPLES OF WHAT YOU HAVE WITH YOU AND MATCH THEM AS BEST YOU CAN.

To replace the weatherstripping in the channels, I used a Dremel Tool with a 1/8″ burr to open the metal channel about 1/2″ – 3/4″, in an area out of the way of the path of the sliding glass
pane.  That gave me what I needed to slide the new weatherstripping into the channel.  Once the new weatherstripping is in place, use a light but complete coat of 995 to bed the fixed pane in place.  Make sure all of the edges are flat, and squeeze it tight.  Very carefully replace the sliding pane in the channel.  Then use a light coating of 995 on the mating surfaces of the frame and the metal bar to replace the bar.  Work the 995 fairly quickly, as the pot time of that adhesive is only about 15 minutes.

Once the window unit is all back together again, make sure as much of the old, failed, original sealant as possible is removed from the frame flanges.  Also clean up the fiberglass.  Dry fit the window frame assembly into its opening, and use blue painters tape to mask the area just outside the finished fit of the window frame.  The painters tape will catch the squeeze out of the new 995.  This makes cleaning up the squeeze out that results from re-seating the window frame much easier.  Remove the window frame assembly from its dry fit position.  Now is is the time to put epoxy fiberglass filler in any of the screw holes that you previously found to be stripped out.

When you’re ready to reset the window frame, get everything you’ll need ready at the work site. Make sure you have the 995, caulk gun and a couple of putty knives, and lots of paper towels. When you’re ready, take a deep breath, say a little prayer, and liberally and quickly spread the entire contents of the 995 sealant tube around the perimeter of the window frame flange. Smooth the 995 to a 30 degree angle (more to the inside, less to the outside of the frame flange) with a putty knife. Then, immediately lift the frame into the fiberglass hole and set the frame retaining screws.  Tighten the screws a little at a time, and do not tighten any of them
fully tight until all of them are under tension. You should get squeeze out of the 995 as the screws are tightened.  THAT SQUEEZE OUT IS WHAT SEALS THE JOINT AND MAKES IT WATERTIGHT.  YOU WANT T SEE THAT SQUEEZE OUT. The blue painters tape will keep the excess 995 from staining or sticking to the surrounding fiberglass. Once the 995 has had a couple of hours to set up, clean up the squeeze out and remove the painters tape.

Finally, you can re-seat the wood trim.  For that, I’d use a polysulfide sealant, like 3M 101, between the fiberglass and the wood.  Or you can use 3M 5200, but 5200 is a very tenacious adhesive which sometimes yellows in the presence of UV from the sun.  I’d use 101.

OK. That’s what I know. I’ve done several of my windows in this way, and I’m very satisfied with the results. No leaks!

Except for 995 to bed glass and window frames, the only sealant material I prefer to use on the boat for bedding wood to wood, wood to fiberglass, or ss to fiberglass, is 101. NEVER, NEVER, NEVER use household silicon on a boat.  It will not hold up, will not take paint or stain, and will NEVER come off whatever it’s been stuck to.  It is a very undesirable product for a boat!