Diesel Engine Maintenance

Diesel Engine Maintenance

by Jim Healy

Diesel Engine Maintenance

When we bought our trawler 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.

Marine Diesel Engine Powered Trawler on the ICW
Marine Diesel Engine Maintenance

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.

Diesel Engine Powered Yachts Rafted
DIY Marine Diesel Engine Maintenance

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.

By Jim Healy from his Blog Travels of the Monk 36 Trawler, Sanctuary

Disclaimer: Curtis Stokes and Associates does not necessarily agree or promote the content by the above author. This content is to be used only with the reader’s discretion.