Two blade in relation to three blade?

[flraptor07]

I hope I can explain this simply, I'll start by example. Say I have a X447 and I want to try a three blade prop, What would be a "rule of thumb" in picking a three blade that is close to the X447 two blade? I'm sure you'll need to go down in Diameter, but how much?

[704Authentic]

...need to know also.

[Fluid]

The old rule of thumb was to choose a 3-bladed prop with 80% of the diameter of the 2-blade. This is really too conservative for a surface drive but it won't get you into trouble. The problem then is one of fiding a 3-blade with enough pitch to maintain speed. An x440/3 would be very safe from a load standpoint, but the lack of pitch would probably mean a slower boat.


.