OK. If your engine turns within the rec Wide Open Throttle that it says in your manual you probably have the right prop pitch.
If your engine EXCEEDS the WOT range you need MORE PITCH.
If your engine is LOWER then the WOT you need LESS PITCH.
There are other lots of propeller options for different kinds of boats. And I hate to say this but it IS a trial and error approach. Some dealers will let you try out props (as long as you don ding it) until you find the optimum for your boat. BUT, the BOAT manufacure should have some data on this. They KNOW what it takes to push that boat. Contact them.
I have a very good book called the "propeller handbook, by Dave Gerr". (got it at amazon) it answers all your questions on props and powering. worth owning it for the serious boater. I look to it first before I dig into my Naval Arch, engineering books and tech papers. This is very easy to understand paperback.
http://www.amazon.com/exec/obidos/tg...books&n=507846