Prop pitch Calculation

[esoxesox]

Hello Boys

I am switching from a Renegade Offshore 17" pitch to an Offshore 19" pitch on my 20' CC (running a 1996 150 Johnson FastStrike). I was previously running a stock SS three blade prop with a 19" pitch. When I went to the 17" Renegade I lost a bit in top speed and could run the tach up a little higher than I liked. My hope is that the 19" Renegade will pull down the RPMs and push up the high end PLUS add the benefits of the 4 blade. I hoped to get it in to run it tonight but it might be a while before I can. Does anybody have a formula that will help predict the change in RPM and top speed? I'm dying to know how this new prop will change the boats performance.

Thanks...

Scot