four blade to 3 blade

[npd4432]

Just purchased a boat has a pirhana 4 blade 14.5 dia 14 pitch prop. The boat has a 2000 Johnson 90 HP. It turns 4800 rpm @ around 28-32 mph. I want to go to a 3 blade. What pitch would get me to around 5300-5500 RPM?

 

[MikDee]

Re: four blade to 3 blade

Just purchased a boat has a pirhana 4 blade 14.5 dia 14 pitch prop. The boat has a 2000 Johnson 90 HP. It turns 4800 rpm @ around 28-32 mph. I want to go to a 3 blade. What pitch would get me to around 5300-5500 RPM?

Just guessing but I'd say a 15" pitch 3 blade. Going to a 3 blade, usually you can increase pitch about 2" for the same RPM, but in order to get your rpm up, I'd say just increasing pitch 1" on the 3 blade should do the trick. In my inexpert opinion.

 

[rndn]

Re: four blade to 3 blade

Sorry, but you need to decrease pitch in order to get rpm's to increase. If you're looking to increase rpm's by 400 you should reduce pitch by 2 inches. In general for every 1 inch of pitch change you will change rpm's by 200. You will also gain some rpm's going to a 3 blade so you may want to try a 12" or a 13" prop.