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Thread: Prop shaft

  1. #1
    Ausfish Silver Member 552Evo's Avatar
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    Prop shaft

    Yesterday I got caught out by a rockwall that extended under the waterline - I was at least 75-100 meters away from the end of it where it made an obvious above water end, but as I found out it must extend out a long way just under water. So the skeg and prop got a bruising, scraping.

    I was in a 10 knot limit zone that was unfamiliar and was rolling along about 8 knots, hit the rocks and stalled the engine.
    The engine restarted fine and with the rush of (oh $hizzen) adrenaline I never noticed anything odd at the time, I moved out to known clear water and turned off the engine, tilted it up and looked for oil and any other damage. It was all good.

    I resumed trolling for about an hour then as I motored out wide for the trip home I thought I felt a vibration as I throttled up to cruising speed.
    Seems to be a small vibration about 2500-3000 rpm. Beyond that I guess the higher revs mask the vibration.
    I'm really not sure if the small vibration was there before and it's normal ?
    Anyway the prop has obvious scrapes and the skeg has obvious scratches and a ding.
    I'll get it checked out by a marine mech but I was wondering:
    The prop is a stainless enertia 15 diam x 15 pitch. Do these bend/distort easily with an impact like I encountered ?
    And how likely is the prop shaft to have bent on a Merc 4 Stroke 150 ?
    I haven't dialled the shaft end but by the eyeball it looks like it may have a wobble by a mm or 2, but again that's the very untechnical method of spinning the prop by hand.
    Thoughts ?



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  2. #2

    Re: Prop shaft

    have you run the engine in gear on the flushing muffs, you might be able to see something that way?

  3. #3

    Re: Prop shaft

    Your insurance may well cover impact with under water objects. Get it checked properly by a respected marine dealer - possibly contact your insurance company to see if there is a process they require to be followed should you wish to make a claim.

  4. #4

    Re: Prop shaft

    Dead easy to bend a shaft with a SS prop, if you get just the right spot and angle.

    BigE

  5. #5
    Ausfish Silver Member 552Evo's Avatar
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    Re: Prop shaft

    Quote Originally Posted by ericcs View Post
    have you run the engine in gear on the flushing muffs, you might be able to see something that way?
    No I haven't, I guess it will be a week until I'm on late shift and I can get the boat to a mechanic so I have a week to do some checks myself. Maybe I'll drop the prop off and get a better view and feel of the shaft.


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  6. #6
    Ausfish Silver Member 552Evo's Avatar
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    Re: Prop shaft

    Quote Originally Posted by scottar View Post
    Your insurance may well cover impact with under water objects. Get it checked properly by a respected marine dealer - possibly contact your insurance company to see if there is a process they require to be followed should you wish to make a claim.
    Yes I'll definitely sound out my options with insurance


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  7. #7

    Re: Prop shaft

    Pull the prop and use a straight edge (steel ruler works)

    BigE

  8. #8
    Ausfish Silver Member 552Evo's Avatar
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    Re: Prop shaft

    Quote Originally Posted by BigE View Post
    Dead easy to bend a shaft with a SS prop, if you get just the right spot and angle.

    BigE
    Ok thanks, yes the prop does seem very hard ( compared to my last tubs alloy one ).
    I'm guessing at 2000-3000rpm there were plenty of right spots
    And the SS ones do look solid and substantial so no give in them I guess. I'll see what happens when I remove the prop and get a better look at the shaft movement.

    On another question, would it be advisable for me to cleanup the small rough edges of the prop surfaces or is doing that a no no without a proper balance ? I noticed from new the prop edges had a flat sharp edge.

    Just saw this you tube video which points out the status quo for me at the 15:30 mark.




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  9. #9

    Re: Prop shaft

    Position propeller shaft roller bearing surfaces on vee blocks. Mount a dial indicator atfront edge of propeller splines. Rotate propeller shaft. Dial indicator movement of more
    than 0.006 in. (0.152 mm) (or noticeable wobble) is reason for replacement.
    That should be doable without pulling the prop shaft out I reckon.

  10. #10
    Ausfish Silver Member 552Evo's Avatar
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    Re: Prop shaft

    Quote Originally Posted by Fed View Post
    That should be doable without pulling the prop shaft out I reckon.
    Thanks Fed Ill give it a go but I reckon the wobble Im seeing could require the decimal point to hop a couple of places

    Im struggling to positively identify the correct part number for the shaft but so far the best I can see is 8M008807 about $360-450 USD.
    Im guesstimating $1000 for the shaft by the time everyone add their cut plus bearings seals oil and labour its going to be at least $1500 probably more.
    At least I can use insurance, I rang and confirmed with them this morning.


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  11. #11

    Re: Prop shaft

    Bugga !!
    Hey, at least insurance may come to the party, hopefully.
    It's just one of those wee things that most have done,, just hope you can sort it with the least hip pocket hurt.
    Good luck with it.

    Col

  12. #12
    Ausfish Silver Member 552Evo's Avatar
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    Re: Prop shaft

    Left prop on and roughly checked the out of round with a dial - I could only contact the machined centre of the shaft on a 45 degree angle with the prop in place.
    So on that angle I measured 0.45mm so it's going to be worse if I accessed it at a 90 degree like I should.

    So I'm not going to bother touching any more of it. Off to the mechanics and get it done through insurance is the best outcome now. At least I know I'll get whatever else needs doing for the fixed price of insurance excess.

    At least nobody was harmed in the making of this exercise, because I did have 3 others on the boat with me when I hit the whatever it was, rock,,,


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  13. #13
    Ausfish Silver Member 552Evo's Avatar
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    Re: Prop shaft

    Insurance was all good and did the claim over the phone so I got a claim number and booked the boat in for next week.
    Be interesting to see if anything else gets picked up for replacement - apart from the shaft, bearings, seals and a prop balance.


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  14. #14

    Re: Prop shaft

    Quote Originally Posted by 552Evo View Post
    Insurance was all good and did the claim over the phone so I got a claim number and booked the boat in for next week.
    Be interesting to see if anything else gets picked up for replacement - apart from the shaft, bearings, seals and a prop balance.


    Sent from my iPad using Tapatalk
    Potentially they will simply fit a new lower unit and prop. That's what happened to a guy I know recently with a Yamaha after contact with a sandbank that resulted in a bent shaft and prop damage. It will all come down to your insurance company and the repairer.

  15. #15
    Ausfish Silver Member 552Evo's Avatar
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    Re: Prop shaft

    Thanks Scottar, as long as it's all back to normal with no ongoing niggles I'll be happy, and wiser for the experience.
    I'll never go back to "that" spot again,,,




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