Hi . Last summer i bought a Fountain Fever 1992 27 whit steeling 13inch extension Box coopled whit Bravo 1 and standard leght Sportsmaster Lower unit 1.50 ratio . Engine is merlin 540ci
i pulled out engine for dyno and make 670lbs torque and 645HP at 5700rpm

The question is how much faster suposed to be ?

i drive last summer whit 28p make 70mph gps at 5000rpm , try 26p and hit 5200rpm not more … if it’s normal ?

The boat is hard to go on the step . Trim table completly down and about 3/4 throtel ..

Trim more up drive to got more rpm’s ?
Drive is about 4-5 on the indicator .

My friends 1992 with a 565ci and Stellings extension box would run 95 consistently. That was well into 700+HP. It needs some trim and between 70-80mph the boat is a handful so be careful. Once on the pad the boat smooths out and is predictable.

I had a -93. Speed with a HP 500 was 71mph, with a 525SC (slightly modified, probably around 550hp) and a -2 IMCO lower it would run 75mph. I would expect you to run in the low 80s with that power.

I bought a B&M 250 W/Nickerson carb, cam setup for a HP500. His package was at 625 HP. It was on a 27 Fever and I believe he was into the 80's with a standard B1.

I solved the problem , today i do some test , i trim more and down table little bit . Hit 78mph gps whit 26p at 6000rpm ! Let’s do some test whit a 28p soon !

I bet you will do well with the 28 if your are turning that 26P at 6K. Update us when you have tried the different prop.