It isn't a 575 Merc. We reused the HP500 block, but pretty much everything else is fresh. Dyno showed peak HP at 5,000. I've thought about raising the rev limiter, but that would require me replacing the distributors (still Merc). If I spend another dime on this project, my wife is going to kill me, so I think I should wait a while....

These still 502's ?

575hp out of a NA 502ci with peak HP near 5000rpms??? That is some kind of recipe and must be a stump puller with a ton of torque.

The 28 vs 30 pitch prop won't matter significantly. The engine torque will have a lot more effect.

Sorry, guys....forgot to mention that they are now 540s. Peak torque is 650 at 3900 RPMs.

Sounds like you could have used a bigger cam.

I had this problem with almost the same horsepower gains. I went from a warmed up 496 with a cam and heads to Raylar 600's. I too started off with 30P but ended back at 28 but labbed them. The performance on to plane was much better with 28's and the acceleration was better. But, in my Bravo breaking abilities I found it better to spin them a bit more than use the torque. Just make sure you are at the top MAX RPM when wide open. If you are close to what you need with the 28's send them to BBlades and have them tweak them and put some cup and or possibly turn them up to 29's so it drops the RPM but gives you gains on the top end. I ended up with a faster prop that felt way bettter out of the hole too. Since you have a similar sized straight bottom V you will benefit from a decent labbing anyway. If one or the other is faster or better, they also might lab the 30 to be smaller too. Its a win/win you just need to pick the better of the two and have BBlades tweak them.