92 johnson 175

i have a 92 johnson 175 that went underwater and is siezed. i figured the engine would need a new powerhead. now, i have heard a few suggestions from have it rebuilt to soak the cylinders in marvel mystery oil. this may sound stupid but, my pressure washer went under also. i pulled the head off the 8 horse honda and poured marvel mystery oil on top of the piston. after a couple days she broke lose. rebuilt carb, new head gasket and now she works fine. i'm no mechanic, but is fixing this engine something i might be able to do myself? if so, where should i start?