Starting point for prop

[TCATTC]

I just got my project boat running. It's a 21' Fisher aluminum deck boat (V hull, about 2600lbs) that I converted from a 3.0 to a 4.3 motor. I tried to find info on what prop came on these boats with no success. I have a 1.98 upper and know I will probably have to change gears. I currently don't have a prop. Any advice would be greatly appreciated.

 

[Sea Rider]

Check with engine manufacturer which prop size would they recommend for a 4.3 ltr engine and your current boat size and load as a starter. Try it at wot while lightly loaded along healthy tach, later can maximize prop to suit your boating needs, carrying loads, general application with one that makes engine to rev around max wot range factory stated.

Happy Boating

 

[Bondo]

It's a 21' Fisher aluminum deck boat (V hull, about 2600lbs) that I converted from a 3.0 to a 4.3 motor. I tried to find info on what prop came on these boats with no success. I have a 1.98 upper and know I will probably have to change gears. I currently don't have a prop.

Ayuh,.... With the 1.98 gears, you can't buy a prop big enough,.... I doubt even a 23" or 25" will be big enough,....

With 1.84 gears, you'll probably be around a 21",..... maybe a 23",....

With 1.65 gears, you'll be 'round 17" or 19",....

I tried all this on my 21' Starcraft Islander,....

 

[TCATTC]

Thanks for the input. I was thinking the same thing about the gears. Mercury's prop selector says to run a 21" for all around performance, guess I can at least try it. the 3.0 had a 17" on it.