blown powerhead?

[RidgeRunner]

Probably went lean and burned a piston. Crap gas and hot weather pre-detonation city.

[phatdaddy]

i don't know how long you've owned the boat or what pm you've done, but before you spend much time or money on the powerhead, i'd make sure you can remove the lower unit. might not be a problem up north, but in the salty gulf, that vintage omc's had a tendancy to freeze on the drive shafts.