I have a 1998 25' invader with 350 GM stearn drive, I believe my transom may be rotten. Do larger boats such as this have wood sandwiched inbetween the fiberglass like smaller outboards do? If so how do I go about getting to the rotted area. I know that the motor and drive unit have to be removed but there does not seem to be any access to where the wood would be. Is this even something that I can handle or do I need to leave it to an expert.