OK it's been pretty dead around here so here is my next project for the winter. My prop center is about 6 1/2" below the pad on my 24' Aero, 24 degree dead rise, 7' beam, bravo 1, 1:36 ratio, nose cone and no tabs, currently Whipple charged 383 sbc, 750hp, current speed with a 21 pitch quicksilver 48 3 blade is 73mph @ 5500 rpm
What should my optimum depth be? If you were doing it, what direction would you take? shortie or recut the transom and move engine up, And how much mph sould I expect?

ttt

If your prop is stock?there is 2 to 3 mph to be gained there ,Not sure about cutting the transom and moving the motor up .Sounds like alot of work and would need to be done perfect,As far as your depth, I am sure others here can help you better than I .Give me a call on your prop and I will gladly let you know what can be done if anything,Darin

It is likely a 23" prop with 17% slip. If it is as 25" you would have nearly 25% slip at your speed. I'm not sure why your slip is so high but you could likely improve that some with a 4 blade prop. It sounds as if your drive is already pretty deep and raising the drive would usually make the slip worse. Someone with more knowledge of your hull and set-up will have to chime in here.

Good luck.

If you are really making 750HP you should be able to turn a much higher pitch than 23 or 25. I haad a pantera, now owned by another member, that was making 600 or so HP with a prop centerline at around 7 below and I could turn a 29p mirage to a speed of 93.4 on gps. Seems to me you might have other issues unless you are banging the rev limiters on your currnet set-up

Scarabman,
I'd like to know more about this Pantera that went 93.4 mph
Length?
Drive?
Drive Ratio?
Exhaust?
CID?
RPM?
Thanks in advance for any reply.
Russ

How much does that boat weigh? Something is not right if you have 750 HP. I've run 74-75 in my 24 Superboat with only 385 HP. I never measured where my propshaft is. I'd go out and get a measurement but my outdrive is off right now. Good Luck.

Dave M.

dave
Setting up a similar boat. Any way you could get me the crank height from the bottom of the boat. What drive do you have and do you have a pad on the bottom. Thanks, Mike

1) Something is wrong with your HP/speed ratio unless your boat is filled with lead.

2) Hard to recommend prop heights when you haven't let us know what trim angle gives you best GPS speed. Generally, you can guess that ANY performance boat application will benefit from a higher drive height if top speed is your only concern but there is much more that comes into play.

3) Finding somebody willing to "rent" you their shorty for testing shouldn't be that big of a deal, especially if you are willing to do it on the offseason.

My guess is that a shorty will help you. You'll need to combine prop changes and testing also, but I think you'll be better off with a shorty.

An Imco +3 box maybe an even better solution, but it will require external steering as well. A shorty and a box are both about the same price, but hydraulic steering is pricey.

I'll go out and try to measure it in a while. I have a V shaped pad with a small single step. Here's a pic.....