38 special
 

520 hp motors turning mercury rev. 4 23 p 4300 rpm's speed 68-70
Would some mirage 25p 3 blades let me spin more rpm's?
Like to turn motors to 5000 rpm's
Baja 38 special

what drives to you have? 1.5 or 1.35? either way, something is wrong, you can not be running 68-70 at 4300 with 23p props. Is that GPS speeds?

Slip #'s on 1.5 drives are -9% at 68 and 2% with 1.35 drives.

seems like your rpm gauges are way off..

Using 1.5 drives and 23p props w/ 9.4% slip (which I get in my 33ol) would put your rpms at close to 5200??

>>>To answer your original question, 25p 3 blades will bring your rpms down lower. Rule of thumb: going from 3 to 4 blade in same pitch should bring you down about 100 rpms where as going from up 2 inches in pitch will bring you down 400 rpms. So in your case bring you down another 300.

if your not using gps for speeds and rpm gauges are correct, you need to try 21p mirage plus (3blade) or 22p bravo 1's (4b)

I will be testing some 24p b1's this sat coming down from 25p M+ to get some more rpms.