Reducing pitch for a 4 blade prop

[AUGIDAWG]

I was looking at this web site, and noticed they recommend reducing the pitch on some of their 4 blade props, sometimes 1-2", or 3-4" for highly cupped props.<br /><br /> http://www.a1discountprop.com/pow-john-evin.htm <br /><br />I called them, and they said they recommend whenever going from a 3 blade to a 4 blade, reduce the pitch by 1" as a general rule. This is because of more area of the prop in the water.<br />Sometimes more than 1".<br /><br />I'm still trying to decide between the 4 blade Turbo 2+2 18" pitch, or the Renegade 17" pitch.<br />I now have the stock aluminum 3 blade 19"pitch on my 95' 200 Ocean runner, running about 5800 rpm.<br />I want less pitch for rough ocean going, so I want to be able to hit 6000 rpm at least.<br /><br />What do you think?

 

[Dhadley]

Re: Reducing pitch for a 4 blade prop

The 3 blade and 4 blade props will run at different X dimensions. If you are not going to dial in the 4 blade thats probably why they recommend losing an inch or so. <br /><br />The 2+2 is a great prop but we've had more success with the Turbo Ultima 4. Still 14 1/4 diameter but different blade shapes. <br /><br />Good luck!

 

[AUGIDAWG]

Re: Reducing pitch for a 4 blade prop

The 2+2 is a thru hub exhaust. I'm not sure about the Ultima 4.<br />A guy at "Propellers Online", just told me that he recommends the Ultima 4, 17" pitch for my application in rough water. The Ultima 4 has bigger and different shaped blades than the smaller bladed "2+2 TH", and from their experiences, is a better offshore prop.<br />I asked him about what would happen to my 5800 rpm. He said it would be about the same as the stock 19" aluminum, because I would have another blade in the water, and it would stay hooked up in rough water a lot better, and produce much better pull and bow lift.<br />I asked how the 18" 2+2 would effect the rpm.<br />He said it would be the same, and that the 2 props have the same equivelent pitch even though they are 1 inch different in measured pitch.<br /><br />Ok, so now that is 2 experts recommending the Turbo Ultima 4.<br />Anyone else have good feedback on the Renegade 17"?<br /><br />Thanks. Time to pull out the credit card.

 

[JB]

Re: Reducing pitch for a 4 blade prop

Moving to General Outboard

 

[AUGIDAWG]

Re: Reducing pitch for a 4 blade prop

I talked to a guy at Dan's Discount Props.<br />He said that the Turbo 2+2, 18" pitch would lower my WOT rpms by about 100 rpm from the stock 19".<br />He said the Turbo Ultima 4, 17" pitch would lower my rpms by 300 rpm.<br /><br />Have you guys noticed this effect from going to a 4 blade?<br /><br />thanks

 

[AUGIDAWG]

Re: Reducing pitch for a 4 blade prop

Well, I bought the Turbo Ultima 4, 17" pitch.<br />The guy at Dan's was wrong.<br />This new prop "increased" my rpm by about 250rpm.<br />I lost about 2mph on the top end, I expected that going to a 4 blade, and the engine runs at 6000rpm at WOT. That is exactly what I was looking for.<br />Now, from a standing start, the boat literally jumps out of the water! The prop must be getting somewhat airborn also, because it revs up to redline for a split second after the initial launch, so I know it's not the vetilating holes. When it sits back down, the prop hooks up and accelerates the boat like a funny car on nitro!<br />I'm on a plane in about 1.2 seconds.<br />The prop does not cavitate in the turns like the original 3 blade aluminum. I can trim it out farther, but then the engine revs about 6200 which is to high for me. I could jack the motor a little higher, but for the offshore application that I am tuning the boat for, I think I will leave everything just the way it is.<br /><br />I am very happy with the new prop, and for only $345.00 plus shipping from Dan's.