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  1. #1
    Join Date
    May 2018
    Posts
    13

    Default Bow Thruster Problem Advice sought

    My bow thruster decided to go on strike last weekend! I can hear the motor spinning but there's no thrust, so my guess is that the shear pin has sheared. Unfortunately I haven't got a manual or any other documentation that might help me to install a new shear pin. One of the key questions is whether or not the shear pin can be replaced without taking the boat out of the water. The unit was installed circa 1996 and is a Technautic bow thruster but I cannot see a model or serial number anywhere. I contacted Technautic who were unable to help except to tell me that these units were supplied by Nobels. Nobels have not yet replied to my e-mail. If anyone can offer any advice about this, I will be most grateful.
    Adrian

  2. #2
    Join Date
    Dec 2005
    Location
    Live London
    Posts
    3,682

    Default Re: Bow Thruster Problem Advice sought

    Usually yes. The thruster connects to a mini gearbox and thatís is water tight. Removing the motor does not least to water in he boat The pin is typically between the motor and the gearbox

    Do bear in mind it sheared for a reason and that may require a lift !

  3. #3
    Join Date
    Nov 2016
    Posts
    359

    Default Re: Bow Thruster Problem Advice sought

    Unlikely that the gearbox to motor pin (if it has one) has sheared - usually it's the prop pin or the prop itself that gets damaged,

  4. #4
    Join Date
    Apr 2011
    Location
    Boat- Western Med
    Posts
    5,085

    Default Re: Bow Thruster Problem Advice sought

    Generally speaking with regards to DIY preventative maintenance

    It’s not mportant to refresh the anode on the gearbox when the boats out of the water .
    If you don,t then the thing corrodes .If that happens at the output shaft(s) , then the seal knackers and you get water ingress .
    Symptoms are a rattle noise ever increasing as the gears rough up = eventually ceasing leading to shear pin # .
    This happened to me with a QL VP type .If it’s an old ish boats there’s parts availablility issues which may end up you needing a whole complete unit .

    Some like say Vetus have a oil reservoir as high up under the bed as possible.
    Idea is a +ve pressure / head of oil so the direction of flow of fluid through the output shaft(s) is OUT .
    Thus mitigating water ingress and above ^^ gear corrosion.
    Now and agian remove the mattress and rummage about to find that reservoir - about the size of a jam jar .

    Yes the internal motors can be removed to expose the top of the gearbox and the water tight through the hull fitting .
    Here you will see the shear pin allready described .Just a couple of three bolts .

    Obviously something like a bag or piece of wood in the tunnel may jam the prop(s) ,,and it may be a one off - tbo that’s wishful thinking I,am sorry to say .

    Msg to everyone with a bow thruster - ck your oil reservoir
    Last edited by Portofino; 11-05-18 at 07:25.

  5. #5
    Join Date
    Sep 2006
    Location
    London/SofF
    Posts
    1,496

    Default Re: Bow Thruster Problem Advice sought

    IMHO it sounds like your shear pin has gone. On my bow thruster this is an easy fix and here is a video of how do it on a different brand, but it might be of help.

    https://www.youtube.com/watch?v=GXH7CvFTsnw

  6. #6
    Join Date
    Mar 2009
    Location
    Home=Surrey / Boat=Hamble
    Posts
    6,208

    Default Re: Bow Thruster Problem Advice sought

    believe its made by Simpson Lawrence, maybe a search with the manufacturers name might come up with something.


    edited bit... can't see anything on google, sorry
    Last edited by Firefly625; 11-05-18 at 08:39.

  7. #7
    Join Date
    Mar 2006
    Location
    Manchester
    Posts
    16,911

    Default Re: Bow Thruster Problem Advice sought

    With our Vetus in 2004-2007, the pin sheared a few times - something like a piece of wood, or similar caused it each time. You just dismantled it from the top down, and the pin was inboard through the shaft that drives the prop.
    Narrowboating From Stretford!!

  8. #8
    Join Date
    May 2018
    Posts
    13

    Default Re: Bow Thruster Problem Advice sought

    Many thanks to all for their comments and suggestions - I am very grateful that you took the time to respond to my call for help.
    Adrian

  9. #9
    Join Date
    Feb 2008
    Location
    Farndon
    Posts
    2,935

    Default Re: Bow Thruster Problem Advice sought

    When my Volvo Penta bow thruster stopped thrusting it was the plastic propeller that had failed rather than the shear pin.

  10. #10
    Join Date
    May 2018
    Posts
    13

    Default Re: Bow Thruster Problem Advice sought

    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!!

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