Welcome to the site!
Before changing the prop, look at the engine setup.
Depending on what performance you want to achieve, raising or lowering the engine on the transom a bolt hole or two can make a lot of difference.
Usually the starting point is to have the cavitation plate even with the bottom of the boat and go up from there. Having the cavitation plate a little over an inch above the bottom of the boat is not uncommon. This will vary greatly with hull design and engine setback. Having one too high will cause overheating and ventilation.
My boat is different than yours, the OAL is 20'6" and I've got a jack plate on it but maybe this thread will give you some ideas.
http://www.wellcraftv20.com/communit...ad.php?t=12543
