Just googled matching propellor to engine, and found this on the Caterpiller marine site:
www.marine.cat.com/cda/files/949240/7/Propellor%20Sizing.pdf
Talks around the tricky subject of matching the prop to engine power available, looks like there will be some more interesting stuff on there.
Have you jacked up the power output from the original set-up, CW?
Here is an extract from the above:
3. "I want more power." If you want to re-engine your boat to increase power and speed, chances are, you’ll need to increase the size (blade area) of the propeller. A prop can only absorb and distribute the power it was designed to handle. For example, if you increase horsepower 50 percent, you’ll probably have to increase blade area 10-15 percent, or cavitation may result. Cavitation is the creation of water bubbles against the propeller blades when it is asked to absorb more than its designed power. This leads to pitting and wear. Ultimately, the propeller won’t be able to demand the amount of power needed (or desired) and the boat will perform poorly.