i bought a 86 chris craft 21 with a 95 evinrude 200 looper and it ran about 15hrs and started knocking pulled the motor and found a bad piston. after we crunched #s we found a 2004 yamaha 4 stroke that we are thinking of buying and put on. can anyone tell me without a doubt what i will have to change and what i can keep as far as wiring( is there an adapter?), contorls, cables and steering. any good solid info will help me make my decision. thanks steve