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Thread: Lost one duo prop

  1. #1

    Lost one duo prop

    So, my boat wasn't responding and handling like it normally does. I knew something was off but I could still drive. Our boats come out for the winter. Sure enough, something WAS wrong. I have duoprops and one of the props on the port side was gone! Other one has a big dent in it like I hit something? I have no idea when or where I would have done that???? Maybe with it being that far back I wouldn't notice? But, it is a pretty big dent and the other one is gone.

  2. #2
    Senior Member easttnboater's Avatar
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    I do not see how hitting something would cause it to completely fall off without damaging the shaft as well. Maybe the nut loosened and the other prop hit it as it went flying off.

  3. #3
    Senior Member Endurance's Avatar
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    My guess is that you hit something that started your prop vibrating. Not enough that you noticed it from the helm, but enough that in time it worked the nut loose. If it came all the way off, it means that there is a good chance that whoever put your props on might have forgotten to put in the cotter key, bend the tab, or do whatever secondary method your props have to keep a nut from coming off. That is a good reminder to all of us to check our prop nut retainers once in a while. Sorry it happened to you.

  4. #4
    Quote Originally Posted by easttnboater View Post
    I do not see how hitting something would cause it to completely fall off without damaging the shaft as well. Maybe the nut loosened and the other prop hit it as it went flying off.
    Hadn't thought of that. That seems a little more likely. I did have a small vibration about the last month or so. Wasn't horrible and with the season coming to an end, I was just waiting. Still not sure what I would have hit to make the big ding in the prop? And, not have known it?

  5. #5
    Senior Member easttnboater's Avatar
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    Something caused the nut to back off. The small vibration might have been caused by running with just the one prop. They are designed to have both props working together.

    The big question now is - Are those counter rotating shafts still running true? If so, then you dodged a bullet and will just have to purchase a pricey propset. If not, then you will end up spending several boat bucks for haul out, outdrive repair, and a pricey propset.

    Let us know how it works out.

  6. #6
    It is out for the winter already. We are up north so they don't allow boats in the winter. April 15 to October 15. Then, on stands in the parking lot for the winter. Going to hvae both lower units taken off and redone. Starboard side is leaking.

    There is a big ding in the remaining prop. I must have hit something? A log or there is also a chance I may have caught the channel marker buoy chain. It is directly behind my boat. I don't think I hit it but where the ding is I had to have been in reverse. That is probably what caused the vibration. I knew it was vibrating but it was only at certain RPMs. So, I just went on the low side and it wasn't bad.

    No idea yet whether things are running true yet. Will have to wait til they get a chance to look at it.

  7. #7
    Senior Member easttnboater's Avatar
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    My boat is on the NC/GA line now on Strom Thurmond Lake. I have closed cooling, so I never had to winterize the engines. But down here, I don't even have to winterize the exhausts.

    Good luck. I hope the shafts are straight.

  8. #8
    Senior Member Frantically Relaxing's Avatar
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    Newer Volvo duoprops don't have a 'secondary' way to lock the rear prop nut, they're just torqued on. The rear prop spins CCW in reverse. If the nut isn't tight, then every time you reverse the prop will put pressure on the nut. That pressure and normal vibration causes it to back out a little more each time. Eventually, the nut falls off, and eventually so will the prop, likely while reversing. If that's the case, it will probably get caught in the front prop, bending the crap out of it...

    When a prop hits something in the water, it usually jars the whole boat because the 'something' doesn't move. The two props colliding with each other will jar the drive a bit until the front prop sinks, but that may not be so noticeable 50' away--

    Sound feasible?
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  9. #9
    Quote Originally Posted by Frantically Relaxing View Post
    Newer Volvo duoprops don't have a 'secondary' way to lock the rear prop nut, they're just torqued on. The rear prop spins CCW in reverse. If the nut isn't tight, then every time you reverse the prop will put pressure on the nut. That pressure and normal vibration causes it to back out a little more each time. Eventually, the nut falls off, and eventually so will the prop, likely while reversing. If that's the case, it will probably get caught in the front prop, bending the crap out of it...

    When a prop hits something in the water, it usually jars the whole boat because the 'something' doesn't move. The two props colliding with each other will jar the drive a bit until the front prop sinks, but that may not be so noticeable 50' away--

    Sound feasible?
    That is a very interesting theory. Seems more logical than hitting something too.

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