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loose prop

Discussion in 'Technical Discussion' started by Beau, Jul 6, 2015.

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  1. Beau

    Beau Senior Member

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    Dsharp thanks,

    Supposedly I am not "riding" the key. The tech/mechanics have done all of the above. I think the best suggestion so far is to change techs and see what happens then. Hopefully, they don't' come loose so I have to go that route, but I doubt it. I'll keep you posted. Any 50 posties or 820 owners, experiencing this? Frustrating and expensive. I've asked my "experts" to just fix it! No relief.
  2. Capt J

    Capt J Senior Member

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    To each his own. If the propellor is installed properly, and everything is correct, there is no situation that will cause the nuts to loosen on their own. Usually you need a 4' breaker bar to get the nuts loose, when you want to remove a prop.

    What will happen sooner or later in your situation, is the shaft will snap off between the strut and the propellor and you'll need a shaft and a propellor. I've seen it happen several times over the years.

    I have an owner who I've dealt with since 2008, with a 2001 50' Post with 820's that ground up his props in the Bahamas, the diver had a terrible time getting the nuts loose and props off.
  3. karo1776

    karo1776 Senior Member

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    This still isn't fixed... seems like a simple enough task...
  4. dsharp

    dsharp Senior Member

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    You could always switch to a castle nut for the second nut. I've changed wheels for years and the only time I've seen one loose on haulout was when they hit something and continued to run it shaking like hell. I've used neverseize on the taper just to help it slide up a little easier. Every yard seems to have a theory on how to install wheels. Have you seen them tighten the wheels? There's a few things to check but it's not rocket surgery.
  5. Beau

    Beau Senior Member

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  6. Beau

    Beau Senior Member

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    dsharp

    Both my marina and prop tech are top of the line, and they seem to have done everything mentioned here multiple times. I haven't been on site for every instance, but I'm confident the work was done with care. Without insulting them I am going to ask for a second opinion from another top prop tech if they loosen again. I do like the castle nut idea
  7. K1W1

    K1W1 Senior Member

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    I didn't see any mention of it but,

    Has the boat ever been aground and really banged the props up?

    Do you get any strange oil leaks, loose parts , things falling off for no apparent reason?

    Are you cutlass bearings wearing evenly?
  8. Beau

    Beau Senior Member

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    K1w1

    Hit some rocks on the Connecticut side about 10 years ago pretty badly. Everything was mic'ed, machined and balanced afterward. No vibrations loosening screws etc. Cutlass bearing were changed about 4 years ago with no uneven wear apparent. Shafts spin true, so they tell me. We will be doing some extended cruising starting next week, so I'll see how this "tightening" holds up. In the past, it has taken some time for the nuts to loosen. Doesn't happen immediately
  9. Capt Ralph

    Capt Ralph Senior Member

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    On the other end;
    How is your clutch coupler set up? Tapered shaft into the coupler or a blunt end captured?
    After your incident 10 years ago and loose nuts for a while now, I wonder if something is not perfect on the other end and fine vibrations come down the shaft.
    Usually if it's a tapered shaft coupler, it would have a single crown nut and a pin thru it or a self locking (NyNut) and a pin above it. I guess you could rotate ends next inspection.
  10. PacBlue

    PacBlue Senior Member

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    Another thing to check is the length of the Propeller Hub, as I have seen some non-standard Prop Hubs that are shorter than the SAE requirement, and therefore do not provide the required contact length along the shaft taper.

    What diameter is your shaft and what diameter is your propeller?
  11. wdrzal

    wdrzal Senior Member

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    Since K1W1 and Karo1776 addressed how to use Prussian blue and how the taper should lock the prop on, I think you need to check the nuts and shaft threads. I would check the threads on the shaft and inside the nuts with a ASME thread pitch gauge (especially in region where the nuts are when they are tightened). Then with a dial indicator check for excessive backlash in both X & Y axis. All nuts on threads have backlash, your looking for more than ASME allows. The threads on the shaft could look not stripped or pulled but a improperly ground bit on a lathe can make great looking threads but out of tolerance.
  12. Beau

    Beau Senior Member

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    Update:

    Knock wood (hitting my head) my prop nuts have not loosened this year. Hurray. Thanks for all your good advice.
  13. Enterprise

    Enterprise New Member

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    According to Steve d'Antonio, you put the big nut on first and tighten it to the proper torque. You then remove it, install the small nut, and then the big not on top. Having said that, I don't go through all that. I lapped the shaft one time and now use a PropSmith to put the props on. I've had no trouble.