Keeping your boat shipshape!
Maintenance · AftLog Blog
How often to change outboard oil
The 100-hour rule, the annual rule, and why both matter for a long engine life.
Most four-stroke outboards call for an oil and filter change every 100 hours or once a year, whichever comes first. Two-strokes use injector oil and have no sump to drain — but the principle is the same: oil is the cheapest thing you'll ever replace on your engine.
Short trips and idling are harder on oil than long cruises, so if you mostly putter around the dock, stick to the yearly side of the rule. Old oil loses its additives — that's what protects against wear and corrosion in a marine environment.
Lower-unit oil is a separate job: typically every 100 hours or annually, and worth checking right after a suspected impact. Milky or metallic oil means water or wear — get it looked at.
AftLog tracks oil changes and lower-unit services per boat and reminds you when the next one is due — find out how.
Track these on your boat with AftLog — free to start, $29 lifetime Pro.