I'm currently spinning a 23" 4 blade Offshore prop( which I just found out is an outboard prop and shouldn't be on my boat. Gotta love my dealer) on my 2000 Stingray 230 SX 454 MAG. I'm running 68-71@5000. I'm gonna pull off the restrictive silencer tips and change to a Bravo 1 four blade. What size should I run to take the best advantage of the xtra HP I hope to gain? Also, what effect does prop diameter have on RPM at WOT?

you should be able to pull labbed 24 pitch bravo with your set-up!!! bill

Yep labbed 24'' is the way to go, smaller diamater = more rpm

If possible go to your prop shop and ask to try different props. My prop guy lets us use them obviously in hopes we will buy 1. Try a four blade 1st, I did not like it on my boat.

Bravo 24p should do the trick. Brother in law had a 220SX stingray with the 350/300hp small block in his and it FLEW! Of course that was 2 years and 2 boats ago. Good luck!