have a 1989 scarab excel 28 including platform am building a 454 .30 over, dart alum. heads air gap alum intake,demon 850 hyd. cam 571-553 thumper thru hull, bravo with a 23 mirage boat weighs 4500 lbs any help on prop and or speed would be great will dyno next week am shooting for 500-600 hp still to cold in mich. for a test ride thanks

Sounds like you're right on target with that engine. Probably closer to 500- 550 hp. 23p prop sounds about right. You might want to try a 4 blade prop. Mirages on heavy boats tend to slip a lot in the midrange.

what's your thought on a nose cone for the bravo ??

I have the exact same boat w/502 mag Msd box ,water crossover,800 double pump crane 139631, roller valve train, gil dry pipes and Imco 2" stubby, best was 72.8 Gps 1/4 tank, Bravo1 24p 5400rpm

The original '89 Bravo gearcase?? A nosecone properly installed probably wouldn't hurt but would do little more than look nicer on the trailer. A nosecone on a later Bravo would probably be a liability since the later gearcase worked great at normal drive heights and speeds into the 80's. I've been paid many times to remove nosecones and clean up the mess on the later Bravos. IMHO Save the time, effort, and bucks, and forget the nosecone. --- Jer

decided against nose cone with just blast drive and re-paint

We can turn your prop into a ACCLERATOR.