They work now.

Well, the new engine makes decent power increases to about 4800rpm then get's stagnant.

Interesting as the cam should pull past this.

What carb ? What timing ? What are your a/f ratios up there ? Fuel psi staying 6psi or more up there ? What exhaust ?

Holley 4150 mech secondaries worked by Nickerson Performance, DUI distributor mech advance with 24deg advance, initial at 12, 36deg total. No issues with fuel pressure..... and EMI Thunder with dry tails.
The dyno sheets were with a Speed Demon carb though... Only quick ride I got this year it ran much stronger and up over 5400 RPM easily but I didnt have GPS on.
No clue on A/F ratios though, as I dont have a gauge/bungs.
If anything I might presume the exhaust is holding back? Or the original carb?

Thanks for all the replies.....

What size BG ? What size Nickerson ?

So, we don't really have much factual info on how it runs now. But rpm is more...that's good..means a little more power up in rpms anyway.

My opinion is that with this engine properly tuned and no ignition or fuel flow issues or air into carb isn't restricted, this motor should peak say around 5600rpm, or so.

Do a better test session with current prop and go from there. If you are not one to watch plugs and try different carb jetting by performace....02's may be in your future. Worked carbs are seldom 'right on' out of the box. A few get lucky.

With 500+ HP you should easily be in the 80's. My 24 Superboat ran 78 with 425 HP. 28P Bravo @5000 RPMs. The boat had a scary chine walk with a Mirage+. It handled pretty nice with the bravo.

Thanks for the all the help SB....
Im in the middle of trying to make some test runs and reading the plugs as well.... I just did a tune up on the motor and all new plugs to make some runs, but havent had a good day for it yet...
I think the BG was an 850 but always ran like crap... Took my 4150 holley that was a 750 and but who knows now that they opened it up for the motor. Ill look when I get home if it says on the paperwork what cfm it opened up to.

Wow.... well sounds like I should maybe try some bigger props.... Im guessing at least a 28P Bravo.... Would like to know for sure if the new Rev4 XP 26pitch or 26.5pitch prop would be good or even work??

How did your 24 Superboat run at those kind of speeds? Did you have hydraulic steering and/or K-planes?

Yes, FULL hydraulic steering and 280 K-planes. When I got the boat it had a 454 Mag MPI (385 HP), and just the external steering ram. The boat ran 73-75 MPH with a 26P Bravo@5000 RPM. It was pretty loose at high speeds. I repowered with a 496HO, completed the steering system to the helm, and was able to go up to a 28P prop. The steering made a HUGE difference. My hull was a '98 which had the small step. More importantly, it had a v-shaped pad. The trick was to balance the boat on that pad. the steering really helped with that.

Interesting.... Ill have to keep an eye out on a deal for a hyd. steering setup... I have got to say my boat is so smooth and no chine walk or loose at that 70 - 75mph range with the Rev4 prop! With the B1 26p it was loose and chine walking too though. I just dont know I want to dump 3-4 grand into full hyd. steering and k-planes when id like to sell and go bigger within a couple years...

I believe the X dimension is different on a Suberboat. I forget what it was on my 24 Sunsation, however the drive was much below the pad. I found that a Bravo 4 blade 24" was the best all around prop. It never chine walked. When I tried a 26", the torque made the boat heal over when the tabs were level. I had full Hyd. steering and was not looking for just top end speed. I was running 650 horse and would run in low 80's with a lil more left. Unless your going to mess with the X dimension, you may be at the optimum for that set up. As others have said-get hyd. steering at those speeds!

Could be FastShafts at my optimum like you said. I l love the Rev4 since it gives me way quicker plane time and adds about 5mph cruise speed one going around 3000RPM up to about 4500 or so... I surely won't give up the cruise efficency and stability to gain 2mph on top end. Only way I'd stuck a bigger prop is if I can maintain the cruising speeds and stability up top 🖒