Keep Your Engine Purring

After collecting your materials, you'll then need to warm up the engine. This does two things: It thins the oil so it's easier to pump, and it gets the soot, dirt, and debris into suspension in the oil so that material can be pumped out with the oil. Diesel engines tend to run cool unless loaded (that is, driving the boat), so you may have to run your motor in gear for a while to warm the oil sufficiently. Remember, the temperature gauge, if you have one, indicates the temperature of the coolant, not the oil.

Once the oil is warm, it's ready to pump. Some marine auxiliary diesels are equipped with a hand-operated, permanently installed crankcase-oil pump. If your engine has one of these, consider yourself lucky; they're a nice touch, but they're regrettably rare. If your engine doesn't have one, you can obtain a portable engine oil pump at most marine chandleries. I prefer the ones that generate a vacuum by pumping; they resemble a bicycle pump, as opposed to the electric models.

Shut the engine down and let it sit for five or 10 minutes to allow as much of the old oil as possible to drain back into the pan. Pump the old oil out either through the purpose-made hose that's attached to the oil drain plug on many engines (don't forget to replace the cap on this hose and tighten it well when you're finished) or through the dipstick tube, then dispose of it properly. Many marinas and boatyards have facilities for accepting used oil, as do local municipal recycling centers. Remove the old oil filter-you may want to wear disposable rubber gloves for this part, and it may require a filter or strap wrench-and place it in a resealable plastic bag for proper disposal. Oil filters can often be disposed of at the same location as the oil. Be prepared for drips and have an absorbent pad in the bilge.

If your filter is horizontally mounted, it's tough to avoid spilling some oil. Oil filters are like screws: They're turned counterclockwise for removal and clockwise for installation. Make sure the rubber gasket comes off with the old filter. Lubricate the gasket on the new filter with clean oil, then screw the filter into place. It should be installed hand tight and snug; there's no need to use a wrench. Finally, add oil to the crankcase until it reaches the "full" mark on the dipstick; check your owner's manual to determine the correct capacity. Then start the engine, and make sure oil pressure is generated either by watching the gauge or by ensuring that the alarm stops sounding-you have a functioning low-oil-pressure alarm, right?-after no more than three to five seconds. Provided you have oil pressure, allow the engine to run for two or three minutes. Shut it down and check for leaks around the filter. After waiting a few minutes, check the dipstick a couple of times; you'll probably have to add a little bit of oil because you'll have filled the oil filter by running the engine. (Remember all that oil that spilled out of the filter when you removed it? Well, it has to be replaced.)

If you treat your diesel to an oil change every 100 hours or once a season, whichever comes first, you'll be rewarded with reliable performance from the parts you can't see-the ones inside the engine.

Steve D'Antonio is a regular Cruising World contributor who offers services for vessel owners, boatbuilders, and others in the marine industry through Steve D'Antonio Marine Consulting (www.stevedmarineconsulting.com).