Winterizing a diesel

From Ocean Navigator #58
January/February 1994
When storing a boat for winter, one has an excellent opportunity to check on the health of a vessel’s engine and related systems. Some procedures described below are fairly obvious, while others are often overlooked.

Diesel engines produce a number of harmful contaminants that are held in suspension by lubricating oil. If allowed to sit in an engine during winter months these contaminants may attack sensitive engine surfaces. To avoid trouble, the engine oil and filter must be changed at season’s end rather than at the beginning of the next.

Before getting to work, the engine should be run until warm. This will ensure that all the old oil drains out. Motors with a turbocharger may have a separate in-line oil filter that must be replaced. Transmission oil also needs an annual oil change. After an oil change, the engine should be run once again for a few minutes, engaging both forward and reverse gears, to circulate the clean oil throughout the engine and transmission.

Consult the owner’s manual to make sure that all grease points are covered. When all other winterizing procedures have been completed, it is a good idea to remove any air filters, squirt a couple of shots of oil into the inlet manifolds, and turn the engine over a few times (without starting it) to distribute this oil around the upper cylinders. Some diesel manufacturers recommend pulling the injectors to squirt proprietary oils into the cylinders, but unless the injectors need servicing, this is more work than most boat owners will want to get into. Air filters need cleaning or replacement, after which the air inlets (and also the exhaust) can be sealed to keep moisture out of the engine. Be sure to leave a conspicuous notice (perhaps on the ignition switch) to remind yourself to remove the covers when recommissioning the engines in the spring.

According to one estimate, 90% of all marine diesel engine problems stem from contaminated fuel. What makes this such an appalling statistic is that fuel contamination is so easily avoided. The primary and secondary fuel filter elements must be replaced at least annually, after which the fuel system will probably have to be “bled” (see the owner’s manual).

When changing filter elements, check the bowl on the base of the primary fuel filter for both water and sediment. If it contains either, not only does it need cleaning, but the tank itself also needs to be drained or pumped down until free of all contamination. In many instances, a tank will have to be emptied and thoroughly flushed. As troublesome as this may seem, it is a fraction of the work and expense incurred as a result of even relatively minor fuel system repairs.

Once a fuel system is clean, the tank should be completely filled. This will cut down on water in the fuel due to condensation during the winter months. After refueling, try to give the tank an hour or two to settle and then draw a sample from its base. If any water or sediment is present, pump the tank down until the fuel comes out spotlessly clean. This eliminates almost all contamination before it can enter the fuel system. Many people like to add a bactericide (such as Biobor-Jr.) to the tank to prevent bacterial growth, but since the bacteria can only survive in the interface between water and diesel, if there is no water in the fuel, there will be no bacteria.The cooling system

Hoses and clamps are rarely given any attention until they fail. This is shortsighted since it takes only a few minutes to check them. Look for bulging, cracking, or softness in the hoses, particularly where hot water is carried, and damage to hose clamps. All clamps should be undone sufficiently to expose the section of the band inside the worm screw housing—this is a likely spot for hidden crevice corrosion. When corrosion is present, the clamp must be replaced, using an all-stainless clamp.

The valve elements should be removed from any anti-siphon valves (vented loops) and washed in fresh water. These valves can plug with salt, allowing water to siphon into the engine or spray over it (sometimes both). A better approach is to remove the valve element permanently, replacing it with a piece of hose attached to the top of the valve. The hose must be vented overboard above the waterline (at all angles of heel).

A freshwater-cooled engine should be drained and re-filled with a 50/50 water/anti-freeze solution. This needs to be done even if the existing coolant already contains anti-freeze, and even if the boat is in the south where it will not experience freezing temperatures. Anti-freeze contains various corrosion inhibitors that are depleted over time and need replacing. In addition, every few years, before refilling the system, it is recommended to flush it with a radiator cleaning compound (available from automotive parts stores).

Draining requires particular attention to low spots. The flexible impeller is best removed from most raw water pumps, in order to stop one impeller blade from being bent against the pump cam all winter long, which may give it a permanent “set.” If the impeller is not taken out, it should at least be lubricated with dishwashing liquid, and its cover left loose (this will stop the impeller from sticking to its housing). The impeller should be checked for cracking of its vanes, or excessive wear (the tips will be flat instead of rounded). Once again, be sure to reinstall the impeller, or tighten down the pump cover, when recommissioning.

The engine should be run for a few seconds to drive residual water out of the exhaust system. Then remove the drain plug from any water-lift-type muffler. All zinc anodes must be inspected and replaced if more than half eaten away. The raw water strainer also needs cleaning. On an engine with a heat exchanger (or oil cooler) with removable end caps, these should be taken off to check for silting, scaling, or corrosion of the “tube stack.” A fouled stack can be rodded out with an appropriately-sized wooden dowel (use caution, however – the tubes are easily damaged). A corroded heat exchanger or oil cooler needs replacing. Finding another heat exchanger, should one fail during a voyage, will probably be both difficult and expensive. And the failure of an oil cooler may cause extensive damage to the engine.

Rather than drain a raw-water system, there is a preferable approach. Close the raw-water seacock and make a routine inspection (as above) of any flexible pump impellers, all zinc anodes, raw-water strainer, and heat exchanger (if fitted). Then disconnect the engine suction line from its seacock and dip it into a bucket of 50/50 water/anti-freeze solution. Finally, run the engine until this solution emerges from the exhaust. The raw water system will then be fully protected against freezing. It should be noted, however, that some states are now mandating the use of propylene glycol in anti-freeze (as opposed to ethylene glycol) and this may damage rubber impellers.

If a boat is left in the water, there must be no possibility of water backing up, or being driven up, the exhaust to flood the engine. If it is hauled out, the screen on the raw-water inlet should be cleaned of barnacles. This is also an excellent time to disassemble, grease, and reassemble all seacocks.Engine exhaust

The exhaust is another area rarely given much thought. There are, however, one or two checks that are advisable. On an engine with a water-cooled exhaust, the hose should be taken off the water injection nipple on the exhaust elbow. Scale or debris in the raw water circuit sometimes forms a plug at this point. Next, the exhaust pipe or hose should be broken loose from the end of the exhaust elbow. There are two things to look for here: excessive carbon formation in the exhaust (it should be basically clean) and corrosion of the elbow, particularly on the bend immediately below the water injection point. (The combination of hot gases, salt water and a relatively sharp bend is a potent troublemaker.)

When heavy soot deposits are present in the exhaust, not only must they be cleaned out, but the engine operation must also be reviewed to find and eliminate the source of the soot. There may be a plugged air filter, or problems with the fuel system, but as often as not on a voyaging boat the soot results from improper use (typically, repeated running at low loads to charge batteries and run refrigeration while at anchor). An exhaust elbow that is at all eaten away needs replacing. If a new one is fabricated, make sure it is welded together, rather than brazed, and that all components, including welding rods, are of the same metal.

Finally, on an engine equipped with a turbocharger, it would be a good idea to remove the exhaust and inlet ducting to expose the turbine (exhaust side) and compressor (inlet side) wheels. These should be clean and free-spinning, with no rubbing on the turbocharger housing. If not, a mechanic will be needed to fix the problem.

Engine and transmission remote-control cables are a common source of operating difficulties. The cables need a thorough inspection. Things to look for are any of the following: corrosion at the end fittings; bending of actuating rods; seizure of the swivels at the transmission or engine; cracks, cuts, burns or melted spots in the conduit sheath; corrosion under the sheath (it will swell up); and excessively tight curves or kinks (the minimum radius of any bend should be eight inches).

It is a good idea to disconnect cables at the engine and transmission. The free movement of both the cable(s) (over the full operating range of the remote controls) and also the engine or transmission lever can then be independently checked. When the cable is reattached, it is essential to ensure that the neutral position on the remote control corresponds with the neutral on the transmission, and that the transmission lever is moving fully into forward or reverse. (Hurth transmissions, in particular, are susceptible to damage if the operating lever at the transmission does not move through an arc of 30 degrees or more in either direction.)

It is quite remarkable how often one sees a boat laid-up afloat on which the bilge pump throws out a steady stream of water every few hours. In almost all cases the source of the leak is the stuffing box. If the battery should die or the pump fail, the boat will sink.

The packing can be pinched up to stop any water ingress. However, if this is done, when the engine is put back in service and first started it is important to engage the transmission at the dock for a couple of minutes and to then shut the engine down and immediately feel the packing gland. If the gland is more than slightly warm, the packing is too tight—the shaft is in danger of being scored. The packing must be loosened again. When a leak through the stern tube cannot be sealed without tightening the packing to the point at which it heats the shaft, the packing needs to be replaced. This should, in any case, be done every year since old packing tends to go hard. It may as well be done at winterizing time on boats that are hauled.Electrical considerations

A battery left in a partially discharged state for a period of months will suffer a permanent loss of capability. Thus, there are two aspects to battery lay-up: achieving a full charge before lay-up, and maintaining this charge during lay-up.

Since the charge acceptance rate (the ability of a battery to take a charge) tapers off quite sharply the nearer it approaches a full charge, if an engine-driven alternator is used to recharge the battery, regardless of alternator size, the engine will have to be run for several hours before the battery is fully charged. A battery charger (depending on type) will most likely require a day or two of operation to fully charge the batteries.

Once a battery is charged, its fluid level must be topped off (unless it is a sealed battery). The battery top needs cleaning (using a solution of baking soda, followed by a wipe with a rag dipped in fresh water) and drying (to avoid electrical leaks across the case). Finally, the battery should be stored in a cool, dry place—the cooler the better, since this slows the rate of internal self-discharge. Depending on battery type, there will still be some internal self-discharge: ‘wet-type’ batteries (those that need topping off) should be put back on a charge once a month; most gel-cell (sealed) batteries can be safely left for several months.

The electrical harness could do with an inspection, especially the starting circuit and, in particular, the engine ground strap or cable (which runs to the battery negative post). Corroded terminals and connections need to be undone, cleaned, re-tightened, and preferably sprayed with a sealant or smeared with petroleum jelly. If a high-output alternator has been installed, make sure the cables are not working loose. In a particularly damp environment, the starter motor (especially its pinion, if accessible) and alternator should be sprayed with WD-40 or something similar. Drive belts need loosening.Reversing the process

Come springtime, many essential tasks will already have been carried out, but there are always one or two more to add to any list. It would be a good idea to separate the propeller shaft coupling halves to check the alignment (but only after the boat has been back in the water a few days if it was hauled for winter storage). Make a close inspection of flexible engine mounts for loose retaining bolts and undue softening of the rubber.

When extended voyaging is planned, the batteries should be given a capacity test to make sure they will not fail at some inconvenient moment – this can be done either with a capacity test meter (an item carried by most automotive parts stores) or by a carefully controlled discharge of the battery to see precisely what is its remaining capacity (unfortunately, this subject requires more space than is available here).

Any engine openings that were sealed at lay-up time will need to be uncovered, the raw-water pump impeller reinstalled (be sure to bend the vanes down in the right direction) and the pump cover tightened. If drained, the raw-water system will need priming. The stuffing box many need loosening. Some boats have the newer rubber-boot type shaft seals. In this case, any time the boat is hauled and then put back in the water, the boot may burn out if it is not primed by pulling it back until water squirts out. Alternator and other belts should be checked for proper tension.

Lastly, the engine needs to be cranked for ten to 15 seconds with the throttle closed so that it does not start. This should be repeated three or four times, or until the oil pressure gauge shows pressure, so as to relubricate the bearings. This is particularly important on motors with a turbocharger. When the engine is started, immediately check for oil pressure, and water discharge from a raw-water cooled exhaust. Idle the motor for several minutes to establish thorough lubrication of all internal surfaces – this will provide time to make a check for any oil or water leaks.

This past year, after a brief lay-up, a local sailor put his engine back in commission. He cranked the motor, and received a head-to-toe shower through the open engine-room door! The alternator, starter motor and electrical harness took a bath before he got the motor shut down. An inspection revealed that rust from the raw-water cooling system had plugged the water injection nozzle into the exhaust, causing the water pump to build up enough pressure to burst the hose.

As it was, the sailor was extremely lucky. Not only did the hose blow at the dockside, but it also had the decency to do it while the boat was in fresh water, so no lasting damage was done to electrical parts. Others might not be so fortunate! By following suggested winterizing procedures, one may be able to avoid dangerous and expensive equipment failure. They will help both to discover many a common problem in the making and to enable corrective steps to be taken at dockside rather than in crisis at sea. It will also keep your engine running sweetly for another year.

Contributing editor Nigel Calder is the author of several books, including Boatowner’s Mechanical and Electrical Manual, published by International Marine.

By Ocean Navigator