OK heres the thing. we have a 39 ocean express cat with aprox. 900 HP a side running through #4 speedmasters an the boat weighs about 10K. we put a pair of 16x28 3 blades on and it blows them out right away ( we expected that but they are the only props we had laying around and new props had not arived yet, couldnt wait to put it in you know ) any way we are trying a pair of 17.5 X 33 4 blade merc lab cleavers. and this thing wont plane or take throttle past about 2000 RPM now. do you think this too much prop and do you think there would be any advantage to airate the prop (with some kind of ducting?) like they do on the race boats with merc #6 drives. i have seen some of them with a large round tube that comes straight up fronm the cavitation plate to introduce air to the prop for help planing. we are trying a set of 16.5 x 31 4 blades today to see if it helps an i just thought i would run this buy you guys while we were out. any thoughts would be great. thanks all

I have a cat with surface drives and 17X29 pitch 3 blade speedmaster props.I have the same problem.These props came with the boat and supposedly the engines turned these fine.I had to replace the engines when I bought the boat(I knew this).Went to the lake and could not get more than 2000rpm and not even close to getting on plane.I did have a bout with bad gas in the tanks and my friend said that I should check the plugs for fouling because he had the same problem with bad gas.When he tried to throttle up he could not get more that 2000rpm.When he changed the plugs everything worked fine.I have not had the time to check the plugs but I hope this is the problem.Anyway let me know how you come out.If you would like to try my props let me know I can fedex them to you.I may need smaller props.Would you possibly be intersted in a trade.Mark
[email protected] 678-522-4873

I was talking to a prop guy the other day about proping my new cat. I brought up my feeling that the bravo was going to be my only prop choice because that was the only prop that would be able to get me on plane. His comment was not to worry about planing as he could "fix that". Don't know how or at what cost, but he was confident that he could get my boat on plane. Guess what I'm saying is that you could try talking to a prop shop about some modifications. Of course by then your new ones would have come in...

hmmm . . .well with the 31's today we got 4000RPM but no plane well, we wil just hafta continue to tweek this thing, may have the x dim too high but it is right where ocean x said it should be. guess this is part of the new boat shake down blues.

i here ya cord. . .i guess if all else fails we will hafts actually talk to somebody that knows what there do'n . . hey any idea waht happened to your concord i swore i saw it in a drive way here in toledo , sure looked like it.

I havn't heard. All of his ads have been pulled. I would have been nice to keep track of the boat. Kinda wish I still had it...sniff, sniff.

Thank's you guys and Dave, Im the one with the 39' Ocean. UPDATE !!!! The drive height is 3/4 of an inch above the bottom and the 17x31 4 blades got us on plain with 3 people in the sponsons and 5600 rpm. Does this sound like not enough prop? Or x demension.
Greg

Do you still have the smaller props the 28" ones