Spilman,
I have a 21 ft Checkmate with a forged 383, AFR (180 Eliminator) heads, Bob Madera cam, and full roller valvetrain. So far I have picked up 21mph from the 350 that was in it when I bought it. If you repower for big hp NA motors, you will spend a significant amount of cash to build 2 stout motors to handle big power. If you want to build blower motors, again you will have to spend some big cash to build motors that can handle boost and HP reliably. Blowers will add complexity and time to the repower. How much time do you plan to spend at 80mph? I built my boat to go 80, but I find that I still drive it like I did when it had the 350 in it, which is mainly cruising. Most people I take out in don't get the same big kick out of going stupid fast that I do, so the boat spends 93% of its life running between 1200-3500rpm. What I am trying to say is that I wanted nothing more than a really fast, loud boat. Now I have a really fast, loud boat, but I am not getting $15000 more fun out of it. Yes I am really proud of my work, proud of how the boat looks, and I like how it turns heads, but having $10,000 more than I have now in the bank would be pretty cool too...

93% running 1200-3500 WOW how true that is.......