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Author Topic: Changing prop from 2 to 3 blades on P31-2  (Read 5874 times)

justbreath

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Changing prop from 2 to 3 blades on P31-2
« on: January 18, 2020, 01:22:31 PM »
I have recently purchased a P31-2 with a yanmar 2GM20F 18 hp diesel. It came with a 2 blade prop. I would like to change it to a 3 blade. has anyone out here done such a change.Can anyone give me hints on how to proceed.
Any info would be most helpfull.
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Last Resort

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Re: Changing prop from 2 to 3 blades on P31-2
« Reply #1 on: January 21, 2020, 09:46:14 PM »
I'd recommend you DON'T DO IT!!!  I did just that and accomplished nothing but losing money on the resale of the 3 blade prop. I lost almost half of my reserve power, and the 3 blades did nothing for my forward speed except produce ALOT of turbulence on my rudder. If you presently have a 16d x 11p (the usual one installed), I would suggest going to a 15d x 11p. I did just that and what a difference. I can now reach RPMs of 3300, whereas before 2600 was the most, and can now maintain at least 4kts against steady waves, whereas before I would get knocked back to 1kt, and I only lost a bit of reverse power and haven't even really noticed any higher fuel consumption, although I'm sure there is :)   If you still want to pursue a 3 blade though, make sure it's equivalent to a 15x11, NOT 16x11 2 blade as I got since there's NO improvement.  Mine was a Campbell 14d x 8p, so maybe try 13 or 13.5. The prop seller will be able to advise you better. 
Good Luck!!!
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