If I measured correctly the crank centerline is 16.5 inches above the bottom of the V. Hope that helps.

Dave M.

I have the straight version 24' Superboat (No pad or step).
The crank centerline is around 18" above the bottom of the V.
That should put the prop shaft about 5" below the bottom of the V.
Dave's prop shaft would be 6-1/2" below with an X of 16-1/2".
I would try a 4 blade Bravo I prop first.
If you feel the need to raise the prop shaft, a shorter than stock drive is the way to go. That way it will be easy to go back...
You may also be better off with a 1:1.5 drive ratio. From what I have read, the lower ratio is only needed when you have a 100+mph boat.
If you really have 750HP, that boat should run over 90mph. The previous owner of my boat hit 85 with a little more than 500HP.
I hope you have full hydraulic steering...

What are you guys smokin?

85 in a 24' vee with a non-ventilated hull, with 500hp????

My little 22ZX Donzi tops out at 76.5 with an HP500. Granted, it has not been tweaked, but another 10MPH?? I don't think so... I gained ~14mph by going from a stock 7.4mpi to the HP500...That is HUGE!!

My boat is the stepped hull version, with a high X.

Now, if your talking speedo readings, then OK. Mine buries the 80mph Gaffrig II speedo now. I mean 80 is in the lower right hand corner, but the needle is aiming straight down...

BUT I'M ONLY GOING 76.. ON A REAL GPS (Garmin eTrex)!!!!!!!!!!!!!!!!!!!!

Arrgghh....

Maybe you should do some homework on hulls before you start doubting people.

My wore out 454/330HP motor with 600 hours pushed my '87 REGAL Velocity to 63mph on a Garman 60C gps this with a Mirage 23P. We'll see what it does in the spring with a 540ci motor. I guess the hull does play a big part....

I have not weighed the boat but it is heavy I'd say 4500 to 5500. I do have external steering. I have not dynoed the engine and was told it should be 750. Who has a dyno simm program that can run these specs?
8:1 CR
5.7 rods
400 crank
dart pro 1 alum heads 230cc intake runners 2.08 int valve 1.60 exh. 72cc com. cham
whipple charger 6psi non inter-cooled
holly 1050 dominator bench flowed for this app.
stock merc ignition
I believe ign. at idle 10 degrees
powerflow exhaust with 4" risers
comp cam hyd. roller
gross valve lift intake .510 exhaust .520
valve timing @.050 intake open 4 btdc close 46 abdc
exhaust 53 bbdc close 3 atdc
cam installed @ 111 intake centerline
duration @ .050 intake 230 exhaust 236
lobe lift intake .3400 exhaust .3470
lobe separation 113
I'm thinking comp sold me the wrong cam?
Friend of mine built a similar engine for his 1/4 miler and got 750 hp but had a way different cam. I specifically ordered this cam for the boat.

Thanks for the imputes, Buck

Hi Buck,
I have desk top dyno at home and I'd be happy to run those numbers for you. It may not be totally accurate without the flow figures for your heads though.
I doubt your boat weights more than 4000lbs.
My 1989 24' Pantera weighed in under 4800 on the trailer with fuel and my Superboat is a couple hundered less than that was.

Mr. Mudball,
I do smoke on occasion, but I also know the difference between Speedo and GPS readings.
My 24' Pantera ran 64mph GPS with a 305HP/7.4 and my 24' Super runs 66mph with a 310HP/7.4MPI. Next year she'll run 75+ with the 415HP/502 I just bought...
Like Dave said, maybe you should do a little research. There is a BIG defference between your FAT Donzi 22ZX and a LEAN 24' Superboat.
There is a 30' Super that just came down your way.
AKA Krakmeup here on OSO.
His boat runs 72+mph with a 425HP/496HO; and YES GPS...

WOW, is all I can say!

I am not familiar with Superboat, but am with many other vees.

That must be one heck of a hull on those boats. They don't sound super light, either!

You have 3mph over my 22ZX with the 7.4MPI. I went a best of 63.

OK, given that you gave your speed with a 7.4mpi, I come up with the need of 400hp to go 75 for your boat...Incredible!!

To go 85, you would only need 515 hp!! MORE INCREDIBLE!!

I used the formula from Bob at FTM, which works for most vees:
((desired speed / current speed)squared) * old horsepower.

Those are very good numbers for the 30 footer with a 496. That boat only needs 600 hp to go 85!! Awesome for a boat that size!!

OK, sorry for doubting!! I'll have to look into those boats when I'm ready for a new one!!!! Do they ride and handle well?

Take care,
Kent

Thanks Patrick, How do I get flow # for these heads? Maybe on Dart's web site?, I'll check and if they are I'll post back,If the cams wrong could you plug some # in and suggest a cam? Thanks, Buck

Hey Kent,
Have a look...
http://www.superboatonline.com/

Buck,
You may find flow numbers on Darts web page.
Another place to look is High Performance Chevy.

Talk to you later,