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Thread: Spun Prop?

  1. #1

    Default Spun Prop?

    I got a 1969 25 hp Johnson 25r69. Heading to the ramp the other day and the thing started slipping during the acceleration like a spun prop. You had to let it get back to idle before it would pick up again. The funny thing is that this prop works with the old shear pins, I can't see how it is possibly spun and the shear pin is intact.
    I got it back home and drained the foot oil and checked for shavings, none. Then i took the gear housing off and everything looked good no worn parts. Next i took the drive shaft out and both ends look fine, no wear. What the heck is going on?


  2. #2
    Fleet Admiral Gary H NC's Avatar
    Join Date
    Dec 2005
    East of Charlotte NC.(Indian Trail)

    Default Re: Spun Prop?

    Really does sound like the prop.I think i would have tried another prop before taking everything else apart.
    Let us know what it ends up being.
    I'm sure some of the pros will chime in on this.

    1981 ChrisCraft 210 Scorpion K,175 Johnson SeaHorse

  3. #3
    Petty Officer 2nd Class
    Join Date
    Jun 2007
    S.W. Georgia

    Default Re: Spun Prop?

    Well, I'm no pro but I've read on this forum to mark a line on the hub portion of the prop and then the prop with a marker. Run it and then check the marks - if they are not lined up then you have a spun prop. It sounds like a spun prop - I had the same problem. The shear pin has nothing to do with it.

  4. #4
    Join Date
    Jun 2006
    W. TN.

    Default Re: Spun Prop?

    X2! On both replies. The prop has poured rubber bushing and when it wears out, the hub with the pin in it spins inside of the hub with the fins. Make sense?

  5. #5

    Default Re: Spun Prop?

    Well thanks for the advice. I'll try another prop, but i thought this prop didn't have the bushing and all that other junk just the pin, therefore it couldn't be spun. I guess i was wrong.

  6. #6
    Supreme Mariner
    Join Date
    Sep 2003
    Cape Cod

    Default Re: Spun Prop?

    That is a very common misunderstanding. I have six 9.5HP motors from the 60's and early 70's and all of those props have both systems as well. The shear pins tend to go when someone shifts at too high RPM or hits a solid object while running. The rubber bushings wear from repeated insult and age - kind of like myself.

  7. #7
    Vice Admiral samo_ott's Avatar
    Join Date
    Jun 2006
    Ottawa, Canada

    Default Re: Spun Prop?

    They are all correct. The inner rubber hub can spin in the outer metal part with the fins. Take it off, make a reference mark and then run it. Then check the mark. If it has moved,the prop is spun. It can be rebuilt/fixed at a prop shop or an OMC place or just find a cheap used one and keep that one as a half speed backup!

  8. #8
    Honorary Moderator Emeritus tashasdaddy's Avatar
    Join Date
    Nov 2005
    Jacksonville, Florida

    Default Re: Spun Prop?

    like this
    Attached Images Attached Images
    TEBOW Country

    Please, NO PM's (Private Messages) regarding boat/engine problems. they will not be answered.
    That is what these forums are for. Post your questions, in the appropriate Forum.

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