Re: boat size
I agree, a V8 of whatever size you want is what is common/desirable/needed. The GM 350 would be the best option as far as price is concerned. You can go up to a big block if you want, but then you have to start looking at engine/bilge constraints and Bravo I drive gear. The 5.7L will allow you to stick with an Alpha drive, which are more plentiful and cheaper to obtain. The 2.5L you have isn't going to cut it.