Wolford

Does anybody here have a guess as to what a Nova 23 would run with a 475hp small block? Is that enough hp to spin a 23 mirage on this hull?

endeavour32

iTrader: (4)

I think its going to be very hard to get that kind of power in a marine application out of a small block. It would be easier and cheaper to build a 475 hp BBC. As far as props, don't get hung up on pitch. Its all about getting the correct prop for your power curve.

Wolford

Well I hear what you are saying, but I dyno'd this engine at 522hp at 6k, that was with dry tube headers though! Maybe I will be closer to the 425-450 range with wet exhaust and all accessories. It's 383cid, with AFR 200cc heads and a host of other top shelf parts. What starting point would you suggest as far as a prop?

dereknkathy

you have about 125 more than a stock 330 hp. the 20hp per mph rule of thumb i think is a little low for a hull that small. i would think mid 60's. 70 tops. 23 or 25 pitch. since you only need one prop, try to find some guys to borrow from for test runs. you might find smaller diameter gets better top end. merc laser as opposed to mirage. i saw 50 once or twice with my chris scorpions and chaparral 230xl. all with 260 hp small blocks. both pretty similar to 23 nova hull.

endeavour32

iTrader: (4)

What cam are you running? I have a feeling you used a big automotive cam which will not work in a marine application. The engine must be able to idle under load at 6-800 rpms. The second issue you are going to have is you're going to need to run long tails and really good manifolds. I built a 439 BBC a few years ago and used all top shelf parts along with 10.25 compression and I was 530 hp. The fact that you made the same in a smaller engine with heads that flow nowhere near BBC heads tell me the the dyno was set to dream-o-meter status. Either way let us know what cam your using and some other general specs. Better yet if you can post your dyno sheets that will give us some good info to help you with. I'm by no mean an expert on SB but there are some guys on here that are. Mr. Fixx All has a lot of experience with them as does Uncle Dave.