If you want to change cam's the mercury HP500 cam would seem the perfect choice, same power and designed for marine use. Huge thing to worry about is reversion, I have wasted a motor due to that... Head gaskets you need to find out what's on there,if not sure and running salt water Change them/ If I remember right after I changed mine I found out they would have been OK but better safe that sorry. If salt water what intake you using- make sure it has the brass lined water passages or that aluminum will disolve from the inside..GOOD LUCK and have fun with it.