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Thread: Yamaha 25 prop selection...

  1. #1

    Default Yamaha 25 prop selection...

    Yep, another thread asking advice on props!
    Been doing some on-river tests with our 16' Aluma Weld Xpress jon with 25 4-stroke Yamaha. I got the Tiny Tach from Cabela's (someone previously pointed that little gadget out on a past thread-thanks!), my hand-held GPS and here's what I found (boat loaded with 2 guys (about 460 lbs.) fishing gear, small cooler, 6 gallons gas; also have Mac's River runner guard on lower unit of motor):

    9-7/8 x 9 prop: WOT @ 5900-6200 RPM's yields 17 mph going upstream (Kenai river)
    " @ " " " " 22 " " downstream " "

    9-7/8 x 10-1/2 prop: WOT @ 4900-5100 RPM's yields 15-16 mph upstream
    " " " " " " 22-24 mph downstream

    Question: does someone know what the ideal RPM range is for this motor (tiller, short shaft, 2002 model)? Not sure but I think the 9" pitch prop is winding out the motor too much, but the 10-1/2 " pitch prop is not letting it get in the correct RPM range; can anyone recommend a prop in the middle? The boat loaded is pretty typical.
    The 9" pitch prop launches the boat on plane quicker while the 10-1/2" pitch prop takes a little longer. I'm pretty happy with the motor as it uses about 1.3 gallons per 12 mile run (approx. 40-50 minutes) WOT; this is 6 miles upstream & 6 miles downstream.
    I called River & Sea today to see what other props they have in stock, currently none.
    Any help would be really appreciated.
    SIDE NOTE: The Tiny Tach was super simple to set up & use, highly recommend it.

    Thanks,
    Jim

  2. #2

    Default

    Anybody? Help?
    Jim

  3. #3
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    Default yami prop

    Speed ranges vary for different models because of different engine operating ranges and different gear ratios. It is generally best to pick the lowest pitch propeller that produces engine speeds near the maximum engine speed ranges shown in your Owner's Manual. The propeller speed ranges shown are only a guide. More accurate information for a particular boat may often be obtained from the boat manufacturer directly or by visiting the Yamaha web site at www.yamaha-motor.com and checking out the Performance Bulletin section. The best way to select the best propeller for a particular boat and customer is by testing various propellers on the boat.
    Try calling yamaha. The custermer service has been great . What lb rating is your boat?..........DB

  4. #4

    Default Bush River travel

    The guys I have dealt with in the bush change props to go up or down stream. Example was when I used an 11 pitch to go down but couldn't get it on step going up. Swapped pitch to 13 and bingo.
    13 would of got me down I know but it's not what I had on at the time.
    As I increase my or decrease my load I change Blades(@ $10 to $15 each) to keep in WOT.

  5. #5

    Default

    DB, not sure the weight rating of the boat, gone till next summer! But it appears Yamaha only has the 2 props available that I already have, and given the RPM numbers, neither is optimal (I think). The 9" (pitch)prop allows to many revs, even loaded, and the 10-1/2" (pitch)prop works okay with 2 guys, fuel, food, fishing stuff; but only able to get roughly 5000 rpms; would like to get to 5500 WOT.
    Seems a 10" pitch prop would be just about right?
    Jim

  6. #6
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    Default

    Quote Originally Posted by Big Jim View Post
    DB, not sure the weight rating of the boat, gone till next summer! But it appears Yamaha only has the 2 props available that I already have, and given the RPM numbers, neither is optimal (I think). The 9" (pitch)prop allows to many revs, even loaded, and the 10-1/2" (pitch)prop works okay with 2 guys, fuel, food, fishing stuff; but only able to get roughly 5000 rpms; would like to get to 5500 WOT.
    Seems a 10" pitch prop would be just about right?
    Jim
    You can always go for an after market prop. Solas has a pretty decent selection of aluminum props. Yamaha says the rpm range should be 5K-6k is safe. I like the upper half of the safe range for WOT. http://www.solas.com/products/propel...randSearch.asp

    I believe that the mercury props will also work if used with a kit.
    Spending my kids' inheritance with them, one adventure at a time.

  7. #7

    Default

    Thanks for the tip Pete!
    Jim

  8. #8

    Default

    Geez, who would've thought a prop for a 25 would be this much fun! Tried Solas, Cabela's; no props with the pitch I'd like. Can you vary the prop diameter a little or do you have to stay with what's spec'd for the motor?
    Jim

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    Default Thanks

    Big Jim, Keep up the good work. You are going to be my goto guy for info on my YAMI 25. HOPE YOU HAVE A GOOD CAMERA....... DB

  10. #10

    Default No Problem!

    This is only our 2nd season using this 2003 motor, but really love it, especially the elect. start! I'm getting to know it pretty well, changed props quite a few times going back and forth getting RPM & speed numbers. Changed oil last summer, I suppose I should get a manual for it (didn't come with the boat package; bought used) to see maintenance intervals.
    Having fun with it; I shoulda done some tests solo with minimal fuel & stuff in the boat; next summer.
    BTW, running 6 miles up from Bing's (12 mile round trip) at WOT (usually) takes about 1.3 gallons of gas. I run premium in it, figure can't go wrong.
    Jim

  11. #11
    Member MARV1's Avatar
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    Default

    Find a Solas prop for it, they have different pitches that would work. A Merc prop will also work, and I believe Honda. Is it aluminum or stainless steel you are using? SS is more consistant and gets more rpm's than aluminum. And also run regular fuel as the Yammi 4-strokes are tuned to run on 87 octane.
    The emphasis is on accuracy, not power!

  12. #12

    Default Hey Marv,

    I'll check again, but it appeared that Solas only had the prop pitch's I already have. Thanks for the tip on the 87 octane, does it hurt to run premium?
    Jim

  13. #13
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    Quote Originally Posted by Big Jim View Post
    Thanks for the tip on the 87 octane, does it hurt to run premium?
    Jim
    Hurts you in your pocket book.
    Spending my kids' inheritance with them, one adventure at a time.

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