Stick to a Schedule
With four-strokes (both inboards and outboards), adhere closely to the recommended oil-change schedule outlined in the owner’s manual. Many marine engines now have electronic reminders — often a small light on the tachometer — that tells you it’s time to change the oil. This interval usually occurs every 100 hours or six months, whichever comes first.
The owner’s manual lists how much oil the engine requires, and it’s just as important not to overfill as it is not to underfill. Too much oil can lead to excessive crankcase pressure, which might blow a main seal. Too little oil can starve the engine of vital lubrication. Have an extra quart or two of engine oil on board at all times, as you might need to add some between changes, particularly with older engines that tend to burn a bit of oil. Check the dipstick before each trip to ensure the engine has sufficient lubrication. Avoid mixing brands and grades of oil.
Always change the oil filter at the same time as the engine oil, as this canister traps dirt, tiny bits of metal and other debris that can damage valve trains, crankshafts and cylinders. Be sure to dispose of oil properly by dropping it off with an authorized recycler.
Two-stroke engines — such as the Evinrude E-Tec, Mercury OptiMax (mercurymarine.com) and Yamaha HPDI outboards — have no crankcase oil to change but do have reservoirs for the oil-injection system that require periodic refilling. A warning light on one of the factory gauges alerts you to the need for more oil. However, all outboards and sterndrives have lower units that need gear oil. Check your owner’s manual to determine how often to change the gear oil. Usually, it’s every 100 hours.
Anglers run their boats much differently than they run their cars or trucks. That’s why your marine drivetrain requires its very own breed of lubricants. If it’s not oiled well, it might not end well.