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  1. #11
    Join Date
    Nov 2016
    Posts
    361

    Default Re: Bow Thruster Problem Advice sought

    Like I said it's almost always the prop shear pin or prop that breaks first.

  2. #12
    Join Date
    Mar 2006
    Location
    Manchester
    Posts
    17,063

    Default Re: Bow Thruster Problem Advice sought

    Quote Originally Posted by DiscoVolante View Post
    Like I said it's almost always the prop shear pin or prop that breaks first.
    You would think they would design the weakest link to be the one inside the boat, given that it's the easiest to get at, and saves lifting the boat out.

    My Vetus internal shear pin was the one that sheared each time there was an issue - (cant remember if it was 2 or 3 times in 6 years).
    Narrowboating From Stretford!!

  3. #13
    Join Date
    May 2018
    Posts
    13

    Default Re: Bow Thruster Problem Advice sought

    Update and some questions:
    I managed to get access to an underwater camera to inspect my bow thruster prop without lifting the boat. What I found was that the prop is still present and the nut holding it onto the shaft is also still in place. So now I think there is a real possibility that a shear pin has gone on the prop shaft and that I might be able to replace it in a couple of hours with the boat lifted in slings rather than taking it onto the hardstand (I'm an optimist!!). Can anybody answer some of the following questions, please;
    (1) Does the Nobels bow thruster have a shear pin on the prop shaft?
    (2) If so what is the spec of the shear pin (so that I can get the correct replacement before lifting the boat)?
    (3) What is the spanner size for the nut that holds the prop on the shaft?
    (4) What is the size of the split pin that secures the nut on the prop shaft?
    If anyone can answer some or all of these questions and/or offer advice on the repair I will be most grateful.
    Thanks in advance.

  4. #14
    Join Date
    Sep 2016
    Posts
    173

    Default Re: Bow Thruster Problem Advice sought

    Quote Originally Posted by AD23 View Post
    Just back from the marina - here's an update;
    I removed the motor from inside the boat and discovered that it connects to the gearbox with a woodruff key instead of a shear pin (it does the same job). It turns out that the woodruff key is not sheared (I have some pics but for some reason I'm not allowed to post attachments???) which means that the problem is further down and it'll have to wait until the next lift out. In the meantime I'll have to improve my boat handling skills!! For the sake of completeness, I should mention that the shaft connected to the motor by the woodruff key, turns very easily and smoothly.
    Thanks again to all who offered advice - you gave me the confidence to get this far!!
    Is it feasible to get a snorkel and mask and a waterproof torch. get down there and have a look while someone turns the shaft inside the boat ?
    previous owner of my boat found a drinks can had jammed in there. Anything to save the inflated prices of lifts as far as I'm concerned.

  5. #15
    Join Date
    May 2018
    Posts
    13

    Default Re: Bow Thruster Problem Advice sought

    Thanks hg2016 for the suggestion but the photo taken by the underwater camera showed that the prop is not impeded by anything.

  6. #16
    Join Date
    Sep 2016
    Posts
    173

    Default Re: Bow Thruster Problem Advice sought

    Quote Originally Posted by AD23 View Post
    Thanks hg2016 for the suggestion but the photo taken by the underwater camera showed that the prop is not impeded by anything.
    Have you managed to spin the prop under the water? Do you feel resistance like it is trying to turn a motor? If not, and the sheer pin or woodruff key is in tact then I think it is likely that your problem could be below the water line. If your camera is of the video type, get someone to turn the shaft and look to see if the prop is turning at the same speed. But going back and reading your post It looks kike you have already worked this out. I'm sorry, but I cant help you with questions 1,2,3 or 4 on your previous post. I'm sure that someone will soon drop in and give you some answers.

  7. #17
    Join Date
    May 2018
    Posts
    13

    Default Re: Bow Thruster Problem Advice sought

    Update:
    I used the underwater camera to make a video of the bow thruster prop shaft and it showed that the shaft was not moving when the thruster was activated. This indicates that the problem is in the gearbox (and not a shear pin as I had hoped!!). Now I'll have to wait until the next haul out to dismantle the gearbox etc. I'll post an update here later in case it might be useful to someone else in the future.
    Thanks to all contributors for their advice and support.

  8. #18
    Join Date
    Jun 2013
    Posts
    3,418

    Default Re: Bow Thruster Problem Advice sought

    Quote Originally Posted by DiscoVolante View Post
    Like I said it's almost always the prop shear pin or prop that breaks first.
    That's not been my experience. Changed quite a few of the inside shear pins, but never one on the prop or the prop itself.
    If found in the Brexit forum, please return to the real world.

  9. #19
    Join Date
    Nov 2016
    Posts
    361

    Default Re: Bow Thruster Problem Advice sought

    All the Vetus thrusters I've seen only have a prop shear pin - nothing internal from motor to gearbox.

    To have a gearbox fail is very odd unless it's very old?

  10. #20
    Join Date
    Apr 2011
    Location
    Boat- Western Med
    Posts
    5,190

    Default Re: Bow Thruster Problem Advice sought

    Quote Originally Posted by DiscoVolante View Post
    All the Vetus thrusters I've seen only have a prop shear pin - nothing internal from motor to gearbox.

    To have a gearbox fail is very odd unless it's very old?

    Common issue see my post #4 - the shaft seals fail and there’s an ingress of water .
    Coupled with neglect of refilling the oil reservoir or overheating as it cools water is sucked in then over time there’s an inevitability of corrosion = bang !

    To the op is there some sort of +ve pressure gravity fed oil reservoir nearby ?

    Of course a foreign body jamming the prop will fracture a shearpin(s) .
    Problem getting parts as said .

    To the Op you not mentioned anodes ? —— there’s should be one on the gearbox either under it directly attached or if a single wheel on the end of the prop bolt ?

    Interesting to see the contents of the gearbox when opened .

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