While the B3 goes for a repair (might be a little time to complete) we have a B1 to install to get out on the water. 24' Spectre Party Cat type of boat. I know the B1 will not get it up on plane as well as the B1 will but it should work if pitched properly. My question is determining the correct prop for the B1.

B3 2.2 ratio with 24Pitch
24 / 2.2 = 10.9

B1 1.5 with a 17P
17 / 1.5 = 11.3
factor in additional slip for the B1 of say %7 more puts you close to 10.9

Am I correct in just reducing this to a math equation to get the prop close or is there more to it? I did find an old thread that references the gears in the upper of a b3 when mated to a B1 lower.
Bravo 3 to Bravo 1 conversion question
See post 15

What power in the boat?

Are you changing the complete drive or just the lower? If lower only then the 2.2 upper will give you a 1.65 Bravo 1

Yes the math will get you close

In any case you can use this calculator

https://www.go-fast.com/Knowledge-ba...lip-calculator

The power in the boat is correct for the as installed 2.2 B3, 5.0 MPI on a 24' cat/deck boat.

The entire drive will be removed and replaced with a temporary B1 at 1.5 ratio.

Was trying to verify that a 17 pitch on a 1.5 B1 would be similar to a 24P on a 2.2 B3, it looks like a 17P will be about right.