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42 searay broken shaft

Discussion in 'Sea Ray Yacht' started by chesapeake46, Oct 31, 2013.

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  1. chesapeake46

    chesapeake46 Senior Member

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    Hi,

    My buddy developed a vibration on his SR a couple weeks ago.
    He was cruising along at around 20 knots in deep water when this occurred.
    He did not hit anything and he assumed he must have picked up a submerged piece of line.

    A week later on a short haul he discovered his shaft was broken between the wheel hub and the cutlass bearing.

    Lucky enough he did not loose the wheel and made it home ok.

    He did not have any vibration prior to the break.

    So, my question is, could this be a result of fatigue or age? He said the shaft was 18 yrs old and maybe it had lived its life.

    I can't buy that and I wonder if there is another culprit.
    I have not seen the victim yet to see if there was an electrolysis issue but I doubt it.

    Can you give us something to look for ?
  2. olderboater

    olderboater Senior Member

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    Maybe rephrase to "He was not aware of hitting anything."
  3. Capt Ralph

    Capt Ralph Senior Member

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    Confusing..



    Old shaft, previous un-known repairs, un-detected D bend, Blem since new, moon phase, unknown collision or a combination of the above.
    A world of possibilities.

    Sure would like some pictures of the fracture. We may be still guessing but pictures could help.
  4. chesapeake46

    chesapeake46 Senior Member

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    Agreed.

    There are lots of crab and eel pots around that he may have clipped but we sorta think he'd have felt it or heard it.
  5. chesapeake46

    chesapeake46 Senior Member

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    I will see if I can get pics.
    Do shafts break unexplainably, often ?

    I've been fooling around in boats for a few decades and never heard of a shaft breaking w/o a reason.

    I would think fatique would mean there would be some shaft movement and vibration that would tip you off to a problem.

    Maybe a keyway cut to deep or too far back ?
    We are not looking to blame anyone, just looking for a "WHY" so as to avoid this in the future.
  6. K1W1

    K1W1 Senior Member

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    Hi,

    Could be any number of reasons including a change in alignment that may be as a result of deterioration of mounts, worn bearings etc.

    If it has failed in an area where they was a machining induced stress raiser ( sharp edge) there has been something that caused the stress to suddenly raise to failure in an 18yr old shaft that has not been previously damaged or over stressed.
  7. Capt J

    Capt J Senior Member

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    I haven't seen a shaft break for no reason either. He could've hit something, had line wrapped around it, or the propellor could've been loose banging on the keyway (which would be my guess), or he hit something.
  8. chesapeake46

    chesapeake46 Senior Member

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    So just because it is an 18 yr old shaft, does not spell doom.

    Not like the tire salesman saying you should replace your tires after 3 yrs no matter what condition they are in
  9. Capt Ralph

    Capt Ralph Senior Member

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    I think a propeller shaft must be the most abused and un-appreciated component of a ships drive line. And still continues to operate with minimum failures.
    Can you imagine the environment, twisting/torque it delivers in both directions, electrolysis and fine vibrations they take?
    Then damage, repairs, adjustments and they go some more.

    It's rare, but It happens, on big & little boats, sometimes they go.
  10. Capt Ralph

    Capt Ralph Senior Member

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    If it was a quality shaft to start with (most are), then age should not be a concern by itself. 18 years of electrolysis and vibrations can ad to its age and contribute to a failure.
  11. NYCAP123

    NYCAP123 Senior Member

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    If there was a manufacturing defect I'd expect it to show a lot earlier than 18 years. Electrolisis could be a culprit, but that will be readily apparent. More likely bad allignment took its toll or he hit something. This time of year, and especially after a storm there's a lot of stuff floating in the Delaware and Chesapeake Bays, and the rivers. I've been through the C&D when at either end you could walk for miles atop the floatsom. Many times I've felt that nasty bang, waited with my breath held for a few minutes feeling for vibration, and conitued on my way forgetting about it when everything felt fine. That doesn't mean there couldn't have been damage within the shaft that's even invisible from the outside. Just part of boating. However I'd take this opportunity to take a close look at the cutlass bearing, struts and the entire drive chain, as well as rechecking my allignment.
  12. K1W1

    K1W1 Senior Member

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  13. NYCAP123

    NYCAP123 Senior Member

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    Very good article K1W1.
  14. chesapeake46

    chesapeake46 Senior Member

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    Yes, thanks,
    I passed this on to my friend too..
  15. RER

    RER Senior Member

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    When a shaft fails (cracks, breaks) between the prop and the strut, I've seen where it's because the prop is not fully seated in the taper - over time the shaft end (including prop) could snap off completely - and you won't necessarily get any warning such as vibration. It's why I don't like to have divers change props in the water.
  16. olderboater

    olderboater Senior Member

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    That brings up an interesting question and that is how often to have haul-outs. My Captains feel that one should do it more frequently than most do, just as a preventive measure in examining everything closely. Obviously the dockyard agrees with that, so can't use their opinion too much since they have a financial incentive. I'd be curious to hear others opinions and practices in that regard.
  17. Capt J

    Capt J Senior Member

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    On a wood, aluminum, or steel yacht, I'd recommend annually.

    On Fiberglass many do it annually, I stretch it to 18 months on a lot of them. Depends on how the current bottom paint is holding up, how much usage and how things were on the last haulout (cutlass bearings etc.), and if the boat is about to take a very long trip.....such as FL to NY etc. This is for South Florida.
  18. chesapeake46

    chesapeake46 Senior Member

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    I looked at both pieces of the shaft last night and took some pictures.
    It looks to me like the prop was not fully seated on the shaft as RER stated.

    Even if you hauled the boat and examined the shaft you would not have been able to see the fracture because it was just beneath the prop hub.

    Between the hub and the strut there is about a 1 & 1/2 inch space, on an inch & 3/4 shaft.

    Also there is a sort of staining on the shaft, beneath the hub that looks to us like the prop was not seated properly.

    I have read, prolly in Chapmans, about lapping the wheel to the shaft but I have never seen anyone actually do it. At least not on these smaller boats.
    I think it'd be easier to do on smaller wheels.

    My buddy also said that the nuts were not entirely super tight when he went to remove the wheel.
    The shaft was all but broken all the way through and he had to bend the remainder back and forth to break it off completely.

    I will post pictures of the perpetrator later today when I've got more time.

    I thank you all for your input. This has been enlightening.
  19. chesapeake46

    chesapeake46 Senior Member

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    I should add that the link provided by K1W1 was very educational for my friend and I.
    I am trying to convince him to loose the Searay and buy a 50 Post......:D
  20. K1W1

    K1W1 Senior Member

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    What is the conversion between this figure and ft/lb or Nm? :D

    I would imagine that en isn't the only thing being lightened with this little escapade.