So I'm mind boggled. When I first bought my boat 00 Bajah2xithad rebuilt low hrs. 509 Sep forged pistons, scatt rods and Arizona speed and marine camshaft M1 4lbs and stock heads. 26 pitch worked over by I don't know who... Labbed prop. Bravo 4 blade. Boat did 72mph @ 6,000ft elevation. So I put on a smallerpulley 6.5lbsboat did 75mph at5,450rpm and running wide band at 13.30 lean.... WellI soldM1bought M3 went out and tried test run on 5lbs. Blew head gasket between 6 and 8. Boat seemed to be flying. Didn't check rpm or speed. So while I was in there and heads off. I thought why not throw some aluminum ones on. So I found some procomps. Through them on with mls gaskets along with roller rockers. Well, with biggerblowerand headsI boughta bravo 28offshelflabbed prop. Went out tuned it on 5lbs. 70mph 4,700 rpms roughly. So I said okay... More boost... 9lbs here we go... Tuned it to 12.6 afr 68mph. I got pissed ripped heads off bought afr 315 had milled to raisecompression. Did leak down test 8 to 10% compression went up from procomps heads of 110 to 145 lbs in each cylinder. So new afr's M3 9lbs 12.6 afr and 34* timing 72mph at about 4,900 roughly. I'm flipping lost. I just ordered smallest pulley. I'm going big or going home. Is this 28 junk? Would it hurt me this bad? Id try my old 26 But soldit likea idiot.... Help me please!

I have been playing around a lot with props lately and found that diameter makes a big difference too. For every 1/4 " I went down in diameter I gained 200 rpm using the same pitch prop. I am running a 24x15.25 4 blade cleaver and the same prop in a round ear will barely plane my boat and runs 800 rpm less. Its amazing how much different props run. I had a 29x14.25 and it took 1200hp in my boat to turn it. Good luck man. Hopefully you can find somone to let you try different props without having to buy them.

Hum... Really has me thinking now... Yeah on the box that my 28 pitch prop came in. It said 625 HP needed. I'm thinking in my head. I know I've got to be Well above that! But then again I'm sure a lot of factors play in to it aswell. Hull design, weight, ect. So... I'm interested in your diameter thoery here. Has me thinking... I wonder if when I went from 26 to 28 that I changed diameters? I Really don't know props to Well. Especially when it comes to cupping...

What is your max rpm suposed to be. If its 5500 then I would say you should have kept the 26p. If its 6000 then I would have gone down in pitch not up. If you went from a 4 blade to a three blade I would have tried a 27p. I have spent my whole summer trying props. I spent a good hour on the first motor trying props and threw a rod bearing. Had to buy a new motor and start all over again. I would figure out what rpm you wanr at wot. For example. If you want 5500 and your running 4900 then drop 3 pitch sizes. You can go down in diameter but If you drop it too much you will lose bite when you start to crest. Round ear props shoukd work good on your boat because you need bow lift. Cleavers work better on my boat because I don't need bow lift. I'm just learning myself through trial and error. Mostly error.

Shooting for 5,500 to 5,600 rpms. And so what size around and pitch you think? And bravo? Or.... ?

Call bblades

I would try and stay between a 14.25 and 15.25 in diameter. Just figure gaining 200 rpm for every pitch size you go down from your current prop size. I would just try and get your max rpms at wot. Its hard to find a prop that will do everything just perfect for you. Like plane off fast and have top speed but if you can find one that works you can tweak it as you go like having it balanced,labbed,blueprinted and they can even progressive pitch it. There are some real experts out there I just never ran across any. Talked to dozens of people on the phone,in person,online and in the end I just had to try different props.

What are you running for exhaust ?

Are you sure you are building that much hp? Maybe there is something messing up your timing or something.

Don't want to sound like a DIK, but heres my thoughts.

First of all, your tuning to a target AFR that is for sure gonna melt $hit. 13's and 12.6 is no where near where you want to be. Try low 11's before moving further.

Your swapping parts and milling heads, changing props and pulleys, and all kinds of stuff.

If you torched the head gaskets, theres a good chance you did some other damage, like hurt a ring land or two.

With your new cranking compression of 145psi, I think you better hold off on the small pulley before you destroy those new AFR heads.

Why don't we slow down, and get back to the basics. Your spending a lot of money to go slower, and breaking a lot of $hit in the process. Glad you ditched the procomp heads too.