Found an easy prop calculator.

[Easyrider]

Dont know if anyones seen this one before-but it has a fair database.

You can input your size/make of engine,make of boat,additional weight + loads more- and it comes up with the reccomended pitch for watersports and speed.


http://www.turningpointpropellers.com/

[three-rex]

results are a bit iffy ... fed my details in ok, and it found my boat, but then the list of possible props started at 14 x 11 !!!

running a 21 at the moment - might step down to a 19, but 11 ??

[Easyrider]

I think the list if props is all the available ones for your engine-it highlights the recommended ones for speed and for watersports.
I did find that it didnt highlight anything for my engine(Tohatsu30) because they didnt do the range of props for it- it only highlighted anything if i put in a more popular engine in the list + added an extra passenger.
I wanted a prop for speed, and i had guessed i needed a 15" pitch-this calculator did come up with this pitch and highlighted it for speed.I know the results were for a different engine-but its only because they dont manufacture a 15" for the Tohatsu, i can get a Ballistic prop though.