Is there a general consensus concerning RPM drop at WOT when switching from a 3 blade prop to a 4 blade prop of the same brand, diameter and pitch.I have a 14.25 X 17 3 blade prop that over-revs by 300 RPM. I want to replave it with a 4 blade prop (same manufacturer) of the same diameter and pitch. I am looking for better acceleration and better grip in the ocean, that is why I want to switch to a 4 blade prop. Will I drop 300 RPM at WOT?
The 4 blade will deliver the performance characteristics you desire. As far as pitch and rpm are concerned, a 4 blade will generally act like a 3 blade of one pitch higher. And one pitch generally equates to about 200 rpm. Soooo, since you seem to need about a 300 rpm drop, I would recommend a 4 x 14.25 x 17P. This wheel will act like a 3 x 14.25 x 18P (a 200 rpm drp, not 300). Since I don't believe 4x wheels come in 18P, your next up is 19P that will drop about 600 rpm, if you can live with these compromises. Your numbers don't work out nicely. I assume you are 300 rpm over the hi-WOT, not the low-WOT. WOT is an rpm range, not an exact rpm. You want to be on or about the high end of the range.
The 200 RPM per ptch change is a "Ball park" figure, its isnt written in stone by no means.I have two props that I run, a four blade turbo 14.5 X 25 and a 14 X 25 High Five. These two props run almost exact same #s, 5,700 RPM. Except that the High Five is a rocket out of the hole and about 2 MPH slower with a fully loaded boat, the one in my avitar. Im not sure that the four blade would even get up on plane if it were not for the Smart Tabs.Things are just not the same as last year, and I cant figure it out yet. Only thing I can say is that Im using a different GPS this year.