i had a 1.50 ratio bravo 1 stolen and found a nice 1.36 ratio bravo 1 drive,question is how much will that change the RPM needed to turn the same prop.
Can I correct by using a diff pitch prop?
Its on a late model 21ft ski boat with a 350 mag 300Hp.
Thanks for any help or suggestions!

You can correct it with a prop. You would need to go down 2" in pitch...that will get you very close. Use this:

http://www.go-fast.com/Prop_Slip_Calculator.htm

only 2?

Ok great thank you.
Looks like a 450 rpm drop so 2-3 degree in prop change.
Thanks!

Thats what the calculator says...Reality may be different. Usually you dont go to a higher ratio until you have ran out of prop pitch in a given line of props.

the only down side will be you may loose acceleration,how fast your boat use to go to a certain mph may be a little longer time to get their..Also you may loose the spap from the engine's power..

For a ski boat and that engine combo, I would not use a 1.36. Its most likely about a 600rpm/3" pitch difference.

I went from a 1.50 to 1.36 and went from a 32p bravo to a 28p bravo. Also I have an almost new bravo 1 upper and two xr lowers that are 1.50 with DWP for sale if interested.

how does your boat run compare to the 150 to the 136 ???

Not as well as mine!

I don't think Mike will know & neither will I. We both changed TONS of stuff, including the drive heights & gear ratios when we re-powered.