Ok i have my 454 out and on the stand looking for an idea like hp numbers and what someone has done. Im right now at 60mph and looking to get 70 or so. I know at 550hp the boat will do 75mph. Y bc the guy before me that had it had it dyno at 548hp. The screw of this is he striped it to stock when i got it. So i know i have a good start b/c the mag has the forged internals and rec heads, 4 bolt main, also have imco thumper series alum manifolds and it will be refeshed to so that helps with piece of mind and maby bore over 30 or 60 if any1 has input on that. Any little thing helps Thanks

Is it a gen IV, V or VI?
I run a ~500hp Gen VI that's 0.060 over (so it's a 468).
You've got a great base to start from, was it NA or Supercharged when it pushed 548hp?
If it was NA and the same cam and heads are on it, what did he take off? If it's just the inlet, put a highrise intake like Dart of Edelbrock Victor Jnr, possibly even a Performer RPM Air Gap manifold and a good (Hollley Marine DP or Barry Grant Demon) carb on it. If you need the cam package, your heads are stock and the bore and deck are standard too, talk to some of the lads here about a whole 'top-end' package to get a matched cam, lifter, head, rocker, intake and carb combo so you know you've got the goods.

Oh, and before anyone else gets in, they'll all tell you to call Bob Mandarra, the Cam Messiah. Believe them, get his number and call him for your cam. HE KNOWS THINGS.

Good luck mate, any more questions just ask. People on here have forgotten more than I could ever hope to learn!

Ok thanks ya its a gen 4 going to keep stock heads and ive got ahold of bob the cam man and we a geting it setup thank for the input.

Good idea, I just received my cam last week from Bob. Use the Moral lifters and Isky springs also. Rework those heads while you have the motor out.

My first thought is just ask the guy what he did and youll be at 75

Sounds like you have a good exhaust system vs the stock Merc exhaust---which is pretty crude. Also, check to see if the heads have been ported. If they have not been ported, then do a MILD bowl/pocket port job and pay special attention to the short side radius, and have a good competition type valve job done to it. If Bob Madara of Marine Kinetics is doing your cam profile then I would say you're off to a great start. Have Fun!