Re: prop diameter
Diameter has less effect on performance than pitch. Generally, within the same prop type from the same manufacturer, increases in pitch result in slight decreases in diameter (1/4-inch or so). Likewise, decreases in pitch result in slight increases in diameter -- again 1/4-inch or so. You are changing from one prop style to another. I don't think that rig was intended to run a 14-1/2 inch prop. I run a 13-3/4 x 19 on a 75HP outboard for example. By taking away 1-inch of diameter you are losing a lot of blade area - hence less "push" and potentially way too high of engine speed. Get the picture?? The key thing to consider here is what performance objective are you attempting to achieve? If your engine operates at or very near its maximum recommended wide open throttle rpm with normal load you already have the optimum prop. Bolting on more pitch will result in lugging the engine and probably a loss of speed and terrible hole shot. Bolting on less pitch will over rev it. If it's not reaching the upper rpm limit, then less pitch is in order. If its already over reving, then you can add pitch and probably pick up some speed but you will lose hole shot.
