Boat is a 223 cobalt condurre with a 425hp merc hp series 1992. Hull is an 1989.

with a mirage plus 23"
5100rpm at 63mph. verified gps and tach 15% slip
3000rpm at 38mph. 16% slip

With a bravo 1 24"
5200rpm at 62mph. verified gps and tach 22% slip
3000rpm at 36mph 20% slip

wot on the motor is 4800 to 5200.

bravo drive is deep like most general sport/run abouts.

The hull really likes positive trim.
What was strange was the bravo would blow out at high trim, the mirage throws a baby tail about 20" tall, but is still hooking up. Trim up/down and speed drops so I can almost say its at optimal trim.

The bravo lifted the stern too much, the mirage lifts the bow as it should just slips too much.

with my old 330 hp the mirage was 11% slip at 59mph. gps and tach verified.

What should I be trying next?

I have been recommended to try a 25" tempest plus.
Will the smaller diameter help with rpms. I know the mirage is a heavy cupped prop, is the tempest similar.


boat is 4200lbs ready to run
20* deadrise
22 feet long, 20 wet

Thanks,

LC

i think that something is wrong that you can spin a 24 bravo faster than a 23 mirage????

I have read that the 24" bravo is less than 24 and the mirage with the heavy cup acts alittle bigger than 23.

i have a baja 272 with a 496 HO i can turn a 23 mirage+at 5050and the best i can turn a 24 bravo is 4800.both prop are stock.

Hello,

First looking at your 23 M+numbers, the cruise slip number you have at 3000 is actually 12.76% (strange that it would be better than the WOT slip #). All of this is of course using 1.5 gear ratio numbers.
For 24 B1's you need to use 23-23.3 for pitch numbers when figuring slip.
I agree the rpm being lower with the B1 is not accurate. I believe something is off or wrong with the Bravo 1 you are running. The higher slip is evidence of this.

Keep the 23 M+ or look at building/ Labbing a 25 M+ or 24 B1 specific to your hull.

Brett

You guys have second guessing my rpms with the mirage test. I know b1 revs are true although I won't be trying that one again. I may have been messing around and wrote down wrong info.

I bought a 23 mirage plus that has had a little pitch added and more cup added. It was cheap. We will try again this weekend

Thanks so far.