Re: what size prop pitch???
4.3 V6 Merc is 4200~4600 RPM.
Well I have a 23p SS prop on my 18 foot bayliner 185 ski boat and my wide open is right at about 4500.
Not sure how big your boat is or what the weight is compaired to my Bayliner 185 ski boat. So its hard to say what pitch to start with.
I also have a 28 foot cruiser with a 21P on a 7.4 Mec so you see just because the motor is higher Hp and bigger doesnt mean a higher pitch works either. This is problably the trickiest thing in boating figuring out what prop to start with.
Maby a 20 21 and go from there once you know the #'s. It would be nice if you could get a few differant props for testing. Whats on the boat now and what are your #'s?