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broken propshaft

Discussion in 'Ocean Yacht' started by Trinimax, Jul 30, 2018.

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  1. Trinimax

    Trinimax Senior Member

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    I am wondering if anybody has the propeller shaft specifications, more specifically the shaft length, for the ocean 43 powered by Yanmars. I checked the owners manual, and it mentions the specs for the volvo powered boats, which had 1 3/4 " shafts. However I have 2 " diameter shafts, so Im not sure if the shaft length is different with the yanmars compared to the volvos.

    I had a similar experience to Pascal, on Saturday, excpet mine was in 2000 ft of water, so no chance of finding the prop. Was running down the coast of Grenada at about 22 knots in calm seas, and then heard a bang and experienced a loss of power on the starboard engine. I then took a dive and found this.(pic attached). There is some damage to the hull near the rudder palm, which I assume is where the prop hit the hull, and the cause of the bang.

    Attached Files:

  2. motoryachtlover

    motoryachtlover Senior Member

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    By no means any kind of expert but have had shafts break and tried to educate myself as to the whys. Hard to tell from the picture but you might measure the distance from the back of the hub of the other propellor to the trailing edge of the cutlass bearing. There is a maximum distance that you supposedly should not exceed. I think it may be a ratio related to the diametor of the shaft. Sorry you gotta deal with this. Last year I had my shafts pulled and xrayed with the blue die (???) and they found one with a crack (at the taper of course) and the other shaft’s test was inconclusive so I had that one replaced as well. We went with Aquamet 22 HD (I think). There is Aquamet 22 and then there is a heavier duty Aquamet 22 we went with the heavier duty.
  3. Pascal

    Pascal Senior Member

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    Sorry you have joined the club...

    I dont know if i followed up on our incident but when i had the other shaft magnafluxed, it turned out to be cracked as well...

    There is indeed two grades of AQ22... regular and high strength (AQ22HS). I was told by the prop shop who machined the new ones that larger sizes (ours Are 3 1/2 ") are always HS.
  4. Trinimax

    Trinimax Senior Member

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    thanks for the replies, I shall definitely be having the second shaft magnafluxed, and I will inquire about the grade of the aquamet. I am tempted to replace the port shaft as well for piece of mind, depending on price. My main challenge now is finding someone to contact for the shaft drawings, since Ocean is out of buisness
  5. MBevins

    MBevins Senior Member

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    Contact whoever you're buying the new prop from , they'll have a supplier of shafts that will have the dimensions.
  6. motoryachtlover

    motoryachtlover Senior Member

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    I looked up what I paid for my shafts back in 4/17 in Florida. My shafts were 2.5” X 197-3/4” long Aquamet 22 HS $5828.00 each. Machine lap coupling tapers $288.00 ea. Machine lap propellor tapers for proper bore contact $288.00 each. Hopefully this will give you a clue of what to expect.
  7. Pascal

    Pascal Senior Member

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    Just paid $7050 for 3 1/2” x 125” AQ22HS with tapers at each end.

    The 2” AQ22HS for my Hatteras were a little over $3000 each with double tapers and 20’ long.

    If no cracks shows with magnaflux I wouldn’t replace the other one.

    Check your manuals almost builders include details on shafts in the drawings otherwise you will have to pull the shaft to measure.
  8. Trinimax

    Trinimax Senior Member

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    Thanks for the reply, I was able to contact one of the engineers from Ocean, who now works at Viking, he was able to supply me with the info i need. The shaft is 2 " by 121" double taper, so I am assuming I should be in the $2000 range.

    Thanks again for the help and I will let you know how it works out.

    I have attached a pic of the damage to the area infront of the rudder palm , where the prop struck the hull. I am lucky that it did not hole the hull.

    Attached Files:

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  9. Boomer

    Boomer Senior Member

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    I was quoted $2700 for the standard shaft on a 46 ocean
  10. cleanslate

    cleanslate Senior Member

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    Darn right Boomer, now we are in the right price range...my eyes were popping at the other numbers.
    Good luck Trinimax, sound like you got it under control.
  11. Capt Ralph

    Capt Ralph Senior Member

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    Always shop for the best, not by bux. If a hd shaft is available, I'd go there. While she is up, have the other shaft fluxed or scaned. Both the same age.
  12. PacBlue

    PacBlue Senior Member

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    The first thing you want to have a shaft with a minimum safety factor of 5.0.
    The shaft supplier should be able to calculate this for you.
  13. cleanslate

    cleanslate Senior Member

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    A simple minded though from a boater who though he knew it all, till I got on Yacht Forms. Anyway is it possible to over tighten/torque the prop nuts over time and causing a weak point in the shaft?
    Like getting to the end of the shaft threads unknowingly while cranking on the prop nuts?
    This is my first time to see a shaft break with out hitting a submerged object.
  14. motoryachtlover

    motoryachtlover Senior Member

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    The experts will chime in. But what I have been told repeatedly is the key seating properly against a properly radiused key way is very important. My understanding is if the prop is riding on the key that stresses the taper which apperantly is the weakest point on the shaft. Metallurgy is not my thing but I know concrete a little and it will likely crack at a corner and I wonder if the key way serves as a “corner” with the metal which makes it a natural weak point. Also you want the bore of the prop and the taper to have as much contact as possible which is achieved by putting an abrasive compound on the taper and installing the prop without the key and spinning the prop. So most of us are totally reliant on a yard and their worker for this seemingly simple procedure but in reality the right way takes more time and knowledge. So at 3:30 on Friday afternoon with it 95 out and the customer is coming tomorrow am to pick up the boat does the prop get installed properly? My experience has been sometimes.
  15. Capt Ralph

    Capt Ralph Senior Member

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    As you can search and find other threads similar to this OPs issue, these same comments come up.
    This time there is a lil key way left on the shaft that MAY point to bad key / prop install.

    Eh, er, ah,,, we all luv to have a reason or a direction to point who / what caused problems like this.
    Old / not so old shafts, never inspected, dyed or fluxed since they were made. Inspected when they were made????
    Prop got dinged two years ago, picked up some weed and a vibration tore it off last week.
    I have come to realize, that shafts take a lot of abuse. It's amazing they don't just cork screw every time the the clutch is engaged.

    Past that; Ship Happens. Things break all of a sudden. Fix it and move on.
    Even if you found something / somebody to blame,, you still lost a wheel and shaft and NO claim.

    Be the better boy scout;
    Have the other shaft inspected and tested well, cracks will probably be found.
    Replace with the best you can find (or afford).
    Years later, it may happen again.

    Murphy luvs boats.
  16. motoryachtlover

    motoryachtlover Senior Member

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    Capt Ralph, I hope you did not take my post to imply that someone must be to blame. I to have noticed our society wants to find someone to point a finger at every time something bad happens. OSHA says there are no accidents only incidents. I find that very hard to comprehend. Like you eloquently said ship happens. Butttt, I have noticed in construction and property maintenance that the person that really likes it done right is somewhat rare. I found a MAN mechanic in SC that is very thorough and every 2-3 years I take it to him and don’t ask him how much it will cost and I pay upon receipt. In other words, I not confident I can find his work and knowledge just anywhere. I have learned that the right way cost more money and that is why a lot of people don’t hire the contractor that wants to do it the right way. Part of what I do is an excavation contractor who tries to do it right and have lost many a job to people that didn’t want it done right or didn’t know what right was. BTW we F up sometimes but we make it right at our expense.
  17. PacBlue

    PacBlue Senior Member

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    And keep in mind that prop shafts are wear items that have limited lifespans.
  18. Pascal

    Pascal Senior Member

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    Prop shafts are by definition under tremendous stress as 100a of HP if not over 1000 HP goes thru a 2 to 4” piece of metal.

    I think how the boat is driven plays a role too, in addition to prop installation Push the sticks forward. Too fast and you re stressing the drivetrain starting with the shafts.

    I learned from this experience. I will get the shafts magnafluxed every 5 years or so and on the first haul out on a new to me boat.

    A few hours of labor is a lot cheaper than loosing a $15k wheel, of spending 3 days looking for it !
  19. Capt Ralph

    Capt Ralph Senior Member

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    No, I did not take it that way and apologize if it came that way.
    Nor did I say just someone to blame ; who / what ; Old / not so old shafts ; lack of inspections ; old damage come back to bite were also included in my rant.
    I'm always sorry to hear of bad luck and bad events. It's good we can share our events and talk about them.
    Just something I wanted to say last thread, or the one before it. I found a window to rant not directed at anybody.
  20. motoryachtlover

    motoryachtlover Senior Member

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    Ralph no apology necessary. I enjoy your posts and as a fellow doer I have felt the blame thing. Didn’t want to come across as one of those that does nothing yet constantly finding fault with the doers.

    Pac Blue I did not know that shafts wear out. What is it that wears them? The torque or corrosion or both?