One more little ditty that may also help you out.

The pitch, the second number in the prop size, is what will set the speed of the aircraft, as well as how well it "pulls".

Think of the pitch as the gears in your car. If you use a lower gear, for instance, your car will accelerate faster, but it will not have a very high top speed, yet the engine is turning very fast. As you change gears, shift from first to second, for instance, you car will pick up speed, but do it at a slower rate and the engine will be at a lower RPM for the same speed as it was in first gear.

So, if you decrease the pitch, you gain power but go slower, but accelerate faster. As my above post pointed out, with a given pitch, and a given RPM, you have the potential of reaching a certain speed. Increase the pitch, you will have a higher speed but less "power" to do it. (your engine has the same power, but it is working harder to turn the prop with a higher pitch than it was with the lower pitch, so it gets to max speed quicker).

CGr.