As long as your outboard is air cooled you should be able to. If if the outboard is water cooled the oil is supposed to be rated for use in a water cooled engine. The operating temps are different and the air cooled oil is supposed to crud up the engine faster than the water cooled oil. And it has been a long time since i have played with outboards so there may be some new magic oil that will work in both but i havn't heard about it.