So I just bought a bravo 1 lower to replace the old bravo 3 due to a failing carrier bearing and leaking shaft seal... But now I need to figure out what prop to go with for the new B1 lower unit...
My boat details:
1995 F-232 LS
Approx. 4300 lbs.
Merc 454 Mag (stock with through-hull)
Bravo 3 upper with 27/32 gears equating to 1.5 ratio with the B1 lower.
Boat has trim tabs that I never need to use.
Bravo 3 top speed was 55mph at about 4800 rpm

Would like to still have decent low end but more top speed... Maybe hit the 60's?
What prop size and pitch should I start with???

Unless your lower is toast, it can be fixed. that said....

Your upper gears with a 1.5 are 32/27 and the lower are 15/19, which are the same as the B1 ratios

Going from a B3 to a B1 your going to get more slip. Being under 60+ mph you may even loose some speed. What ever pitch prop you were using, get the same pitch and find the largest diameter. Can also look at more blades (4 and 5) but this does give you more lift and that can bring its own problems or fixes

Ratios

I'll guess a REV 4 21 would get you real close to what you want or a Mirage Plus 21-23.
Good Luck

I would start with a 23 Mirage Plus prop.

Trust me these smaller Formulas love the Rev 4 prop with the extra bow lift. Whatever pitch you use do yourself a favor and try a REV 4.

it says 28p on the bravo3 set

also yes on the gears and ratios you mentioned... and I looked into fixing it (doing it myself and paying a shop) and the price was near the cost of a new B1 lower from SEI. I prefer the simplicity of a B1 lower and really don't think I need the B3 for a 23' boat... Also the ease of prop change as well with the B1