I have a 1996 26' Scarab with a blown 502 that made 800 hp on the dyno about about 5800 rpms. I have a standard bravo upper with -2 sportmaster lower with a gear ratio of 1.36 I believe. I have tried a 28p Bravo 1 prop that was labbed. Not sure by who. Was able to turn about 4750 rpms with 4 people in the boat and a tank of fuel (about 80 g). I called BBlades in the past and he recommend a 25p Revolution 4 prop. Tried that today with only 2 people in the boat and about the same amount of fuel and only turned 5100 rpms. I can't seem to understand why I can't make this boat turn any rpms. I checked the throttle cable and the carb is onpening all the way. Any ideas why I can't seem to get and speed out of this boat?

Thanks for the help

Was the boat speed the same? I'd start with calculating some slip numbers. What is the GPS speed at the rpm stated?

GPS stopped working. Thinking I need to change the gear ratio.

buy a cheap hand held gps. you need to know your speed or everything a guess.

Will do.

Ditto on getting some accurate gps speed readings to go along with the rpms.

I highly doubt you need you change gears. You should be able to pull the 1.36's just fine with a decent prop. Spinning a 25 with a 1.36 is about the same as spinning a 28 with a 1.50.
I run labbed 24's with 1.36's bolted to 502mpi's to 5100rpms for about 74mph.

Check your timing first.
What size fuel lines do you have running from the tank to the carbs?????? For 800hp you should be running at least a 10AN split to 8AN's for each carb.

Wait... 800hp on a standard bravo..?

Which drive is it?