The three blade is the one he is referring to. Anytime you go up in pitch, you are going to lose RPM. I was told by a prop shop that it is more like 200 to 300 RPM lower for every 1 pitch increase. But that is for 3 blade to 3 blade pitch changes.
I replaced the 3 blade aluminum on my Alpha One gen II, with a 14.5 pitch 21 Dia. SS 4 blade. I had a significant improvement in plane time, and sustaining it at lower RPM. Original 3 blade was 15.5. Thought the price was steep, but after 2 seasons I think it was a steal.
Each inch of smaller pitch will increase rpm by about 200. Losing the 4th blade should also gain you another 100 rpm. You also need to look at the diameter of the props. Every 1/4 inch larger in diameter lowers the rpm by about 100 rpm. <br /><br />I am estimating you will lose about 1.5 mph by going to the new prop. It is hard to say how your holeshot and planing rpm will be affected since a 3-blade generally has greater slippage until plane is reached. This might be overcome by the smaller pitch though...
