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  1. #1

    Default Please review my yamaha 25hp 2 stroke prop and performance

    Today i took my new to me boat out for the first time and ran a baseline. The hull is a princecraft resorter 14.5 long 73" wide aluminum V with a 2005 yamaha 25hp 2 stroke. The prop is stock 9 7/8x11 1/4. I ran 29.4 mph when i trimmed out the motor and rpms were spinning 6050. Verified with a tiny tach and gps. For weight i had myself, my dog and 6 gallons of fuel. Combined weight i would guess at around 660-700 with boat and motor included. I ran a calculation online and it said my slip was .0479 Can i get a bit more out of this motor with a different pitch? Prop is aluminum. Boat planed very easily and maintained plane at 2800 rpms. I would appreciate your guys help.

  2. #2
    Chief Petty Officer
    Join Date
    Aug 2007
    Posts
    449

    Default Re: Please review my yamaha 25hp 2 stroke prop and performance

    I'm not 100% but I think the recommended WOT rpm range on that motor is around 5500.
    That being said your over at 6050rpm anf could probably go up at least 1 pitch probably 2.If you stay at the top end of the recommended range you will probably gain 2-3 mph.I didn't do your slippage but your number seems alittle to good to be true,might have a look at it later.
    Last edited by pootnic; June 27th, 2012 at 08:34 PM. Reason: must be drinking

  3. #3

    Default Re: Please review my yamaha 25hp 2 stroke prop and performance

    Just looked at my manual and wide open range is between 5000-6000rpm. If i go with a stainless prop like a powertech sra3 would i have a hard time turning a 12p? I know the 3 cylinder yamaha 25's have the power to turn them, but my 2 cyclinder might not be up to par of the 3 cyclinder model.

  4. #4
    Supreme Mariner
    Join Date
    Apr 2002
    Posts
    16,757

    Default Re: Please review my yamaha 25hp 2 stroke prop and performance

    Very hard to tell what results will be with a different material. It depends a lot on the effect on the hull if the prop can get the boat up better it could result in more speed and some rpm. But if it loads the motor too much the rpm could be lost resulting in a wash.
    But it does appear that with a 300 rpm change with an al 12" would also be a wash for speed and
    it appears that a 11.25 ss prop could easily over rev. With about a 5% slip it seems unlikely that you can improve on that.
    I've convinced myself that if your going to gain some speed without over revving a 12" ss prop may be the key.
    You might check out the Turning point Rascal and Hustler props.Aluminum with close to ss performance.
    I think they have a calculator.

  5. #5

    Default Re: Please review my yamaha 25hp 2 stroke prop and performance

    Thanks so much Steelspike

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