Tinkerer

I bought this boat and after extensive clean up got it on the water three times this summer. After talking to Bob Leach at Eliminator He tells me the prop shaft should be 1 inch above the lowest part of the back step. I have a -2 inch shorty on it now and am building a -3 shorty for next summer.( Bob told me to stay away from the -4 drive.) This will put mine at 1/2 inch above. The question I have is with a surfacing prop should I still be running a 4 blade Bravo or would a 5 blade Maximus work better OR should I be running a 4 or 5 blade cleaver?
The last time I had it out I was able to trim back down after the boat was flying without losing speed and RPM. The boat is running a Bravo 28 - 90 MPH at 6000 RPM. The new drive is going to be 1:36 ratio so as to bring the RPM back down ( I plan on going up to 800 / 900 HP also ) but I am over the power band of the cam - I should be running approx.. 5700 RPM

jspeeddemon

If that boat is like the one I had, it responded well from a standard to -1 inch shorty, to the tune of about 6 mph, and another 4 mph with the -2 inch shorty! About 850HP will make that boat run 110-115MPH, with a Bravo 1 30 or 32 and a 1.36 gear, depending on motor peak power.

Tinkerer

I have a -2 inch shorty on it now and in driving it I feel the drive needs to be shorter. I have been told by someone that knows to stay away from the -4 drive. With the -3 the prop shaft will be 1/2 inch above the lowest point of the sponsons. I have been told that the ideal prop shaft height is one inch above. I also was going to build the -3 drive with a 1 : 1.36 ratio but was told to stay with the 1 : 1.5 for better acceleration.

abones

I think it depends at what speed you would like to have the hard acceleration pull at . It is impressive to pull hard at or over 100 MPH and unless your motor will run happy at 6k and over I would suggest the 1.36. JMHO.

dmann

I have had a couple 25's with similar power. The one with 1.50 took for ever to come on plan and would cavitate. It took too big of a prop.

jspeeddemon

You definitely want the 1.36 gear with a 30 or 32 prop if you have 800-850 HP. That will put you at about 6000 RPM. The -2 worked well on that boat, not every drive heighth is the same on these tunnels, they vary somewhat by intended use of boat. You can tell original factory position by distance between rubrail and top of gimbal. Original power in the boat was M-4 Procharger motor with a 1.50 and a 32 prop, it would crank 6500RPM.