do you use the same figures for slip on a b3 as on a b1, and is there any difference for twin application, working on a 32 searay cruiser and can't figure out what the slip is or if the numbers I have are correct.4300rpm,1.81gr,22p,30mph, slip comes out to 39%, is that right. boat weight,12,500lbs, T-vortec 350's with 4bbl's, It's a pig out of the hole.
any Idea's?

Prop slip is prop slip but 39% does sound a lot high for a bravo three they tend to run in the 10% or a litle less range
as far as the hole shot s concerned you are at the bottom of the rpm range for those engines and reducing prop pitch will increase rpm and also improve holeshot.

You sure about the ratio? Should be 2.2 ideally or 2.0, 1.81 is used on a big block

1.81:1 is stamped on the upper, I can't find any markings that make me think they have been changed for high alt. I advised the customer that I thought 2.2:1 gears would help him alot across the board, I just wanted to see what you guys thought about it. thanks for your input.