Prop Size?
 

I have a 1988 22' steve stepp velocity with a 454 bored .30 over (420hp and 500 ft lbs torque) with a bravo 1 drive geared 1.50. I was running a stock 23p 3 blade mirage ss prop and getting 35 mph @ 3000 rpm's and 64 mph @ 5000 rpm's. I put a 27p 4 blade hydromotive quad IV prop labbed and cupped and ran 45 mph @ 3000 rpm's, 73 mph @ 4200 rpm's. The prop is too much, all I can get is 4200 rpm's. I was thinking and was told a 25p prop would be the right prop. But not sure. Also not sure if I should get a 3 or 4 blade. I need to be running around 5000 rpm's. Any info would be greatly appreciated. Thanks

Ok,

The 23 Mirage was running the R's you need and at 11.84% slip (good). Also 64 mph, makes sense.

The so callef 27 Hydro was running 4200 at 73 mph which produces a slip % of -1.97%... Impossible.

I love those boats and we used to use them at Mercury Racing for testing. Although, we used most as outboard applications.

Labbing a 25ish 3bl will give the best top end while customizing a 4 blade will be a great all around option. Call us and we can discuss the options.

Brett

Gotta love those negative slip numbers. I need that in my life.

Read the thread and had a little thought.

IF the speedo and tach did indeed read these numbers. Could there be an issue with tach and/or speedo, needed to be checked before dialing in? Of course the hydro could be waaay off in pitch, too. Something like 31"+ in pitch.

Carry on:drink:

Something is wrong. Speedo, tach or both. Is the speed GPS or guage? My 23 Regal/Velocity had a 454 mag with headers. Best prop was a Mirage three blade, 25 inch. On a good day with a light load it would do 70/71. I tried some Hydro 4 plades and the Mirage was always the best.

prop size
 

I'm gonna look at the tach and check it. As for the speeds, all the speeds for both props were on GPS but the rpm readings were on the same tach which appears to be a older tach. It may be off. I did get 72.6 on the GPS with the 27p hydro. The tach was reading 4200 rpm's. It may be off though. Will probably check that out next