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F60 RPM out of whack post collision with tree

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  • F60 RPM out of whack post collision with tree

    Hello,
    Own a 2006 F60 that is acting funny since I hit the lower unit on a tree stump. There was a ding in two of the prop blades (aluminum), but the problem persists wit the new, undamaged prop. There is clearly something wrong, and best I can describe it is the RPM's are not in sync wit the thrust.
    Main symptom is there is a marked jump from ~3000 RPM to 6200 RPM, instead of the more steady climb that I encountered pre-collison, and this jump will happen anywhere from 2/3 to full throttle. It almost feels like a gear shift on throttle up, except with a lag in thrust. It will eventually reach top end speed @ 6200, but it seems to take longer, and the speed vs rpm is real inconsistent, especially at the higher ranges. Will reverse and idle fine. Just a little rough spot where I hit the tree on the front of the lower unit, and the skeg was not impacted.
    Any thoughts on the problem are much appreciated.
    Thanks,
    DG

  • #2
    prop slipping is the only thing I can think of, but that does not fix itself

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    • #3
      Thanks 99
      I think I sort of freaked out a bit due to a few stupid things I did lately. I went out to catalog exactly what the problem was, and I think everything is good now. I changed from a 13 pitch aluminum (the one I damaged) to a 14 pitch stainless, and things just behave different, but not broke.
      Merry Christmas

      DG

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      • #4
        possible cavitation if the RPM goes up but the speed does not.
        prop spinning but not biting the water well due to exhaust or cavitation.
        If it is opposite(long time for RPM to rise) then that prop may not be the best for your set up

        different props do act differently
        you went up in pitch and the SS probably has more cup ,so should be like you changed the pitch even higher.
        some come with holes to inject some exhaust to help the prop slip at 1srt to get the RPM up

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        • #5
          Thanks 99yam40, just getting back on here. I'll go full throttle to 6000 rpm to ~30 mph then I can back off and run ~5400 rpm at 35 top end with high trim. Funny, the rpm will drop to 5500 from 6000 at full throttle on its own, even if I don't back off. Kinda feels like a gear shift, but I guess it is cavitating and will catch on its own? Hard to gradually throttle up to get top end speed, so I'll just live with this for a while.
          I have a new prop related post about a Yam 225 VMAX that has spun hub issues at high RPM, 4200 or less is the safe zone.

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          • #6
            You still have some stuff going on there. You might have the wrong prop on there which can cause cavitation - or you might be ventilating from not trimming the engine properly or you have the engine mounted too high... or damage or something on the hull bottom creating a disturbence. Either way, something is amiss - damage... obstruction... user error... something.
            2000 Yamaha OX66 250HP SX250TXRY 61AX103847T
            1982 Grady Weekender/Offshore (removed stern drive & modded to be an OB)

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