1976 18cc with 1984 140 hp evinrude?

[Bushwacker]

If it's the older cross-flow version, those are simple lightweight motors, but I think they got the old 135's up to 140 hp by moving the rings closer to the top of the piston, which makes for a pretty thin top land. Definitely check the compression before you buy it. Don't think it will tolerate any detonation, so I'd be sure to run premium fuel, decarb it fairly often and don't put too big a prop on it! If it'll rev to at least 5500, you should be ok.