4 blade propeller question

[Hawaiian]

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.<br /><br />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?

 

[JB]

Re: 4 blade propeller question

Prop topic.

 

[mmainelli]

Re: 4 blade propeller question

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.

 

[LubeDude]

Re: 4 blade propeller question

The 200 RPM per ptch change is a "Ball park" figure, its isnt written in stone by no means.<br /><br />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.<br /><br />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.

 

[procraft180]

Re: 4 blade propeller question

Turbo makes a 4 blade in 18p