jimh wrote:Also, the smaller diameter dimension for the CYCLONE 4 propeller is mostly due to the blades being raked aft. If the blades on the CYCLONE were not raked, then the diameter of the propeller would be larger.
I don't buy this. The thrust would tend to fall off the end of the blades soooner on the smaller diameter. That's why I believe the VOLUME of water displaced is more efficient than the VELOCITY of the thrust. No amount cupping or rake will make up for diameter, as the aforementioned characteristics only affect velocity of the water column, not the size.
The Mercury REV4 prop mentioned is 14 5/8" diameter vs your 14.5" Cyclone vs my Powertech OFS4 15 1/4". I suspect the REV4 prop would compare nearly identically to the Cyclone due to the like diameters. Also, if you look at the props, the Powertech seems to have an "elephant ear " shape featuring larger blades.