Spring Commissioning: The Diesel

Most of us sailor types would rather fuss over the rigging and the sails than service that big chunk of metal in the engine room, but it’s also the case that most of us turn to the diesel in times of need, and any engine will have its time of need. Spring commissioning is such a time. It’s also true for the outboard. Here is how to be your engine’s best friend, and it comes with a tip: As you go through the list below, there are many opportunities to replace worn or suspect components. Many of these are service items for which you should have spares aboard. As you call those spares into service, replace the spares—K.L.


1. Drain the engine coolant (if you didn’t drain it last fall) and flush the system. You should have two coolant changes on hand. One is going into the system now; the other will be your backup.

2. Replace any engine zincs that are half-gone or more. You can use the spares that you have onboard. You do have spares on board, don’t you?

3. Squeeze hoses and check clamps. Replace any that are suspect in any degree. No soft spots allowed in hoses, no brittle spots, no corrosion, no cracking. For replacements you can use the spares that you have onboard. You do have spares on board, don’t you? Whenever you install a hose or tube, whether in the engine or the galley or head, smear a light film of grease on the inside of the hose to make it go on easily, seal completely, and come off when you ask it to.

4. Check the joints of hoses and tubes to make sure they have proper support at all points where support is needed.

5. If your engine has an air filter, change it.

6. Check oil filters. For a cartridge-type filter, pay attention to seating the O-ring gasket, and top it off with clean oil. For the spin-on type, spread a thin film of oil over the gasket (thin means thin) and hand-tighten.

7. Check drive belts for proper play, no more or less than inch between pulleys. (Too tight and they wear; too loose and they slip.) Replace any belts that are going slack or showing wear. Look carefully for cracks on the inner surfaces. You can replace with spares that you have on board. You do have spares on board, don’t you?

8. Check the fuel/water separators and drain water as necessary. If filter elements need to be cleaned or replaced, clean or replace.

9. Pump impellers—inspect them, especially impellers on raw-water pumps. Replace any losers from spares onboard. Surely you have . . .

10. And if the engine doesn’t turn over when you ask it to, your first check, probably, would be the battery terminals for corrosion. It takes very little corrosion between terminal and cable clamp to cause a problem.

11. When the engine does turn over, and you’re ready to run it under load, pay attention to the color of the exhaust. Blue smoke tells you that oil is being burned in the combustion chamber, and you probably have worn rings, worn valve guides, or perhaps a clogged crankcase ventilator. Black smoke indicates an imbalance in the fuel-air mixture. Either too much fuel or not enough air is going into the firing chambers, or perhaps you have a new prop and it’s the wrong prop. Black smoke can also be caused by clogged air intakes or a poorly adjusted fuel supply system.


1. Change the spark plugs.

2. Check your tanks, and replace them if they are corroded. Squeeze the bulb and the rubber tubing and replace if they have soft spots, brittle spots, or cracks.

3. Check the trim cylinders for leaks.

4. Check the lower unit for the color of the lube oil Cloudy oil indicates a likely lead around the prop-shaft seal, which should be repaired before you change the oil.


Go sailing.

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