Marine Engine Oil Changes:
How to Change a Marine Engine
Without Spilling a Drop
Most of us who are at least reasonably sane dread the notion of changing an engine's oil and filter because the procedure has a reputation for being such a hot and messy job. But the truth of the matter is, it doesn't have to be nasty. Here are some tips on how to get the job done quickly and cleanly.
Most savvy do-it-yourselfers know how important it is to drain crankcase oil when it's still hot from the day's running. That's because hot, well-circulated oil holds any impurities stirred up in suspension. So, naturally, it follows that a great volume of those impurities and sludge drain away with the spent crankcase oil. Conversely, with cold oil, the impurities settle to the bottom of the oil pan, where they stay until the next time the engine is run. You should also know it's absolutely vital to change crankcase oil during fall lay-up because, otherwise, the naturally occurring acids in the old crankcase oil will have all winter long to etch away the precision-machined surfaces of the crankshaft journals, rod bearings, cylinder walls and piston rings. Long story short, old oil shortens engine life even when the engine is not running.
As for the oil change proper, instead of clumsily crawling around in a crowded bilge on all fours and reaching an exposed arm around a toasty-hot engine, use an oil extractor. Many different brands and models are readily available at marine and auto supply stores. How they work is as simple as the sea is salty. Poke a skinny, hollow probe down the dipstick tube or the oil fill orifice. Pump the pump and the vacuum created inside the oil changer siphons the hot, easy-flowing oil right out of the crankcase sump. The dirty oil is stored in the pump's integral reservoir until its ultimate disposal in an environmentally friendly manner at a recycling center. These days, it's relatively easy to find an oil and dead battery recycling center. Inquire where you buy oil, at your marine engine dealership or, for the computer literate, do a Google search.
Next, slip on a leather glove to protect your hand from the oil filter's latent heat. Remember, we're changing the oil and filter while the engine is still hot! Break the filter loose with a dedicated oil filter wrench. For the paltry few dollars they cost, they are well worth the investment. Don't make the shade tree mechanic's mistake of hammering a screwdriver through the filter in an attempt to lever it off. If you do, lots of oil will drip into the bilge, ruining the clean hands oil change.
Another trick of the trade: Put a quality (thick) quart-size baggie around the filter to capture any lubricant that dribbles out around the filter base when you upset the filter. Also, put an oil-absorbent mat directly below the filter. Sometimes I use a shop towel, but I prefer a dedicated oil-absorbing mat or cloth, the kind that are good for capturing spilled gasoline, diesel or oil. That way, the mat absorbs any droplets that escape from the baggie.
With the preparations out of the way, spin off the loosened oil filter. Pull it free, then seal it in the baggie for its eventual trip to a recycling center, along with the spent crankcase oil.
It's time to add a few quarts of new oil to the crankcase. Since the crankcase oil was extracted from the top of the motor, you don't have to track down the oil pan drain plug and drop it in the bilge a few times in a frustrating attempt to screw it back in place.
If you don't know which particular blend of oil is best for your engine, do the obvious: Consult the owner's manual. If it has gone missing from the boat, call the engine manufacturer's toll-free help line. It doesn't pay to scrimp on oil quality. Marine-grade crankcase oil contains certain additives, such as corrosion inhibitors, that better allow a marine engine to reach its full allotted lifespan.
Unscrew the plastic cap on a quart of oil and begin pouring. While using a funnel is neater than free-pouring, free-pouring and dabbing up the few errant droplets of oil with a shop towel is less trouble. And there is something therapeutic about sopping up a little bit of oil. Once the prerequisite number of oil quarts are in the engine, pull the dipstick and make sure the oil level is at least up to the quart low mark. Was it five quarts to full or six?
Fill the replacement oil filter with oil so that from the first turn of the crankshaft the engine benefits from a steady stream of oil. Otherwise, with a bone-dry filter, the oil pump has to first fill the filter before it can flow oil downstream to the crankshaft bearings.
Before replacing the filter, first dab a fingerful of oil on its black, rubber base gasket. That simple step helps it seal more securely. Tighten the filter on its base, but remember that one day you or someone else will need to remove it, so not too tight.
Double-check your work, then start the engine and run it at a slow speed in neutral for a few minutes. While it's running, examine the oil filter, making sure it is not leaking around its base. After a few moments, turn off the engine and pull the dipstick to see how close the crankcase oil level is to the full mark. If it misses the mark, top off as necessary.