i have a 98 25 foot active thunder with a 500 hp

with 12 inch extention box

i am running a 26 pithch 4 blade predator prop lab finished

at 3500 rpms it does 38mph at 4000rpm it does 46 at wot it does

71mph at 5300 rpm on GPS.

I just put on a 26 pitch bravo 1 prop right out of the box, it had a plastic insert u had to put inside it.

At 3500 rpm with the bravo it does 47 mph and at 4000 rpm it does 54mph at wot it does 68 mph on GPS at 47oo rpm i have seen several boats like mine with the 500 hp using the bravo1 26 prop and they r doin 77 to 81 MPH and spinning the prop 51 to 5300 RPMS any help would really be appreciated. It is 9 mile an hour faster till it goes up over 4000 RPMS with the bravo prop.

first it sounds like you have a power problem, the old HP's have a valve spring problem which causes hp loss. have your engine checked for compression and leakdown. After this you will most likey need new valve springs. Your motor when operating properly will turn a bravo 26 lab finish 5300 rpm, many of the racers are turning 28's.

You should be faster than the 68mph, but i doubt you will hit 80mph. Gordo (F1-51 One Vision)has a 25 AT with a light race lay up and raised X. His boat radared at 81.7 at the LOTO Shootout last year. He would be the one to talk to.