How often should you change a marine engine's oil?

Oil is the lifeblood of the engine, and at sea it works in harsher conditions than on the road. Changing it on time is the cheapest thing you can do for your engine.

The practical rule

As a rule of thumb: every 100–150 running hours or once per season, whichever comes first. An engine that does few hours still needs its oil changed every year, because oil ages and absorbs moisture even when it isn't used.

Marine oil, not car oil

Marine oils are formulated to withstand moisture, salt and long periods at constant load. Using automotive oil is a saving that costs you dearly.

Change it warm and at the end of the season

Used oil carries acids and water; leaving it inside all winter causes corrosion. Change it at the end of the season, not at the start of the next one.