3 to 4 Blade RPM Change Expected

Ernest T

Ernest T

Petty Officer 1st Class
Joined
Aug 29, 2009
Messages
367
If I go from a 3 blade to 4 blade prop with no change in pitch, how would this change the RPM. What if I drop 1 in pitch going from the 3 blade to the 4 (17p 3 blade to 16p 4 blade). Presently running 5800 max RPM with 3 blade 17p ss prop on Yamaha F150.

Thanks
 
L

Leardriver

Petty Officer 1st Class
Joined
Oct 7, 2008
Messages
373
Re: 3 to 4 Blade RPM Change Expected

All prop designs are not the same, but if all else were equal, you would lose 150 rpm.
 
Ernest T

Ernest T

Petty Officer 1st Class
Joined
Aug 29, 2009
Messages
367
Re: 3 to 4 Blade RPM Change Expected

I'm looking at a Powertech prop. I've heard that when calculating pitch with their props, you have to add 1 to the pitch (for example a 16 pitch would run more like a 17 pitch from another manufacturer due to the design of the blades).

I've sent my specs. to Powertech and they have given me 2 prop choices: either a 15p or a 16p 4 blade ski max (MQ4) series prop. I'm trying to decide which one to go with. I was worried that the 15p would result in too much RPM increase (I'm already pretty close to the max at 5800 RPMs with 6000 the recommended max with my current 3 blade prop).

What do you think?
 
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