Bow Thruster Problem Advice sought

I had exactly the same issue earlier this year with precisely the same symptoms. I also used a camera to check prop was still there, then put on the mask and snorkel and it was clear the prop was just spinning on the shaft. When removed on dry land the drive pin had corroded and sheared. Cost of a new pin was just £3 from JG Technologies for my MaxPower thruster. Luckily for me this happened before the boat's annual lift, but otherwise a PITA. I think it would be difficult to do the repair underwater with snorkel. With the right bits and tools it's literally a 10 minute job to replace on the MaxPower unit and could certainly be done in slings.
 
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No oil resevoir. No anodes - but this is a steel boat in fresh water with plenty of aluminium anodes on the hull, some of which are not far from the bow thruster.
I agree that it will be very interesting to see the contents of the gearbox and I suspect you might be right about the shaft seal and an ingress of water.
I do not plan to lift her in this lovely weather, so it will be a while before I can post the answers to all of the questions and suggestions etc.
 
This story has a happy ending. Last week I took the boat out of the water and removed the bow thruster with the help of my ever willing nephew! When I dismantled it I discovered that the pinion gears are held on the vertical and prop shafts using roll pins and that the roll pin on the vertical shaft had sheared.
The shafts, pinion gears, seals and bearings were all in excellent condition. The gear box was still full
of oil. I replaced the roll pin (cost of 1 euro!), reassembled the gear box and filled it with gear oil and
it was ready to be reinstalled in the boat. Total time from start to finish of 4 hours.
For the benefit of anyone with one of these Nobels bow thrusters the following details are provided;
The fibreglass cover on my bowthruster says Technautic but it was actually manufactured by Nobels.
Both the vertical and prop shafts have woodruff keys instead of shear pins. The woodruff key on the vertical shaft can be accessed from inside the boat when she is in the water.
There are 4 grub screws which must be removed before the end caps on the prop shaft can be removed.
After the prop shaft has been removed the vertical shaft can be removed using a punch through the oil plug hole.
For extra strength I replaced the damaged roll pin and then put a smaller roll pin inside the new roll pin (known as a double roll pin).
If you need parts, motor, carbon brushes etc contact info@rimex.nl
Thanks to all who read and contributed to this thread.
 
AD23 said:
This story has a happy ending. Last week I took the boat out of the water and removed the bow thruster with the help of my ever willing nephew! When I dismantled it I discovered that the pinion gears are held on the vertical and prop shafts using roll pins and that the roll pin on the vertical shaft had sheared.
The shafts, pinion gears, seals and bearings were all in excellent condition. The gear box was still full
of oil. I replaced the roll pin (cost of 1 euro!), reassembled the gear box and filled it with gear oil and
it was ready to be reinstalled in the boat. Total time from start to finish of 4 hours.
For the benefit of anyone with one of these Nobels bow thrusters the following details are provided;
The fibreglass cover on my bowthruster says Technautic but it was actually manufactured by Nobels.
Both the vertical and prop shafts have woodruff keys instead of shear pins. The woodruff key on the vertical shaft can be accessed from inside the boat when she is in the water.
There are 4 grub screws which must be removed before the end caps on the prop shaft can be removed.
After the prop shaft has been removed the vertical shaft can be removed using a punch through the oil plug hole.
For extra strength I replaced the damaged roll pin and then put a smaller roll pin inside the new roll pin (known as a double roll pin).
If you need parts, motor, carbon brushes etc contact info@rimex.nl
Thanks to all who read and contributed to this thread.
Click to expand...

Hi there. Great off you to actually post up what the problem was in the end so many posts don’t have the final results !!

Regarding parts. Did you actually get hold of the above email and get parts from them ?
I have e mailed with no response.

Cheers.
 
Thanks for your kind words - I gave the details of my repair in the hope that it might be of help to someone else with a similar problem.
Yes I did get a reply from info@rimex.nl and they offered to help with parts if necessary - as it turned out I did not need any parts from them (just a roll pin which I got in the local motor factor's).
 
Yes - the last e-mail from them was end of April 2019.
Perhaps they are on holiday - you might need to be patient??
Best of luck, I hope you get it sorted.
 
AD23 said:
This story has a happy ending. Last week I took the boat out of the water and removed the bow thruster with the help of my ever willing nephew! When I dismantled it I discovered that the pinion gears are held on the vertical and prop shafts using roll pins and that the roll pin on the vertical shaft had sheared.
The shafts, pinion gears, seals and bearings were all in excellent condition. The gear box was still full
of oil. I replaced the roll pin (cost of 1 euro!), reassembled the gear box and filled it with gear oil and
it was ready to be reinstalled in the boat. Total time from start to finish of 4 hours.
For the benefit of anyone with one of these Nobels bow thrusters the following details are provided;
The fibreglass cover on my bowthruster says Technautic but it was actually manufactured by Nobels.
Both the vertical and prop shafts have woodruff keys instead of shear pins. The woodruff key on the vertical shaft can be accessed from inside the boat when she is in the water.
There are 4 grub screws which must be removed before the end caps on the prop shaft can be removed.
After the prop shaft has been removed the vertical shaft can be removed using a punch through the oil plug hole.
For extra strength I replaced the damaged roll pin and then put a smaller roll pin inside the new roll pin (known as a double roll pin).
If you need parts, motor, carbon brushes etc contact info@rimex.nl
Thanks to all who read and contributed to this thread.
Click to expand...

Good news that you got it fixed, and good that you came back to tell us. Hopefully it will help someone else in the future :)

Can I ask what you mean by a "roll pin", as against a "shear pin"? They sound very similar and, given that a roll pin had sheared, perhaps do the same job?

Can you get at the roll pins whilst in the water?

Presumably, when you refer to a Woodruff key this is different to the roll pins.

I only ask because, on a boat I used to own, there was a shear pin easily accessible from inside the boat, which sheared a few times when something like a piece of wood got sucked into the hole and jammed the propellor. As a layman, it would have been easy to call this pin a roll pin. I ended up buying a few shear pins and taping them to the inside of the housing where the shear pin was revealed.

Did you get a blow up diagram of your thruster..... perhaps a parts diagram, or similar?
 
The roll pin cannot be accessed without taking the boat out of the water and dismantling the bow thruster's gear box. My bow thruster has 2 roll pins (one on the prop shaft and one on the vertical shaft) and their job is to secure the pinion gears on the shafts. Because they are so difficult to access, they are definitely NOT the equivalent of the shear pins!!
The 2 woodruff keys (I think they are identical in size, shape etc) play the same role as shear pins on other bow thrusters. One of them connects the prop to the prop shaft and is under water. The other one connects the motor to the vertical shaft and can be accessed from inside the boat without taking it out of the water. These woodruff keys should shear (hopefully the one inside the boat!) if something fouls the prop as you describe.
Unfortunately I did not get any diagram of my bow thruster - such a diagram would have been very useful.
I suggest using Google to get images and descriptions etc of "roll pins" and "woodruff keys".
BTW I am a layman too and never heard of a "roll pin" until I opened the bow thruster gear box with the help of a more knowledgeable friend :-)
 
AD23 said:
The roll pin cannot be accessed without taking the boat out of the water and dismantling the bow thruster's gear box. My bow thruster has 2 roll pins (one on the prop shaft and one on the vertical shaft) and their job is to secure the pinion gears on the shafts. Because they are so difficult to access, they are definitely NOT the equivalent of the shear pins!!
The 2 woodruff keys (I think they are identical in size, shape etc) play the same role as shear pins on other bow thrusters. One of them connects the prop to the prop shaft and is under water. The other one connects the motor to the vertical shaft and can be accessed from inside the boat without taking it out of the water. These woodruff keys should shear (hopefully the one inside the boat!) if something fouls the prop as you describe.
Unfortunately I did not get any diagram of my bow thruster - such a diagram would have been very useful.
I suggest using Google to get images and descriptions etc of "roll pins" and "woodruff keys".
BTW I am a layman too and never heard of a "roll pin" until I opened the bow thruster gear box with the help of a more knowledgeable friend :-)
Click to expand...

Interesting..... shame the roll pin sheared, and not the correct woodruff key. i wonder if that was unlucky, or a design issue.
 
AD23 said:
The roll pin cannot be accessed without taking the boat out of the water and dismantling the bow thruster's gear box. My bow thruster has 2 roll pins (one on the prop shaft and one on the vertical shaft) and their job is to secure the pinion gears on the shafts. Because they are so difficult to access, they are definitely NOT the equivalent of the shear pins!!
The 2 woodruff keys (I think they are identical in size, shape etc) play the same role as shear pins on other bow thrusters. One of them connects the prop to the prop shaft and is under water. The other one connects the motor to the vertical shaft and can be accessed from inside the boat without taking it out of the water. These woodruff keys should shear (hopefully the one inside the boat!) if something fouls the prop as you describe.
Unfortunately I did not get any diagram of my bow thruster - such a diagram would have been very useful.
I suggest using Google to get images and descriptions etc of "roll pins" and "woodruff keys".
BTW I am a layman too and never heard of a "roll pin" until I opened the bow thruster gear box with the help of a more knowledgeable friend :-)
Click to expand...

Woodruff keys are not roll or shear pins and are not designed to fulfil the function of shearing as they are merely a method of attaching a parallel (or tapered) shaft to another bore of the same shape and transmitting the full power from the shaft to the bore, often with a lot of contingency.

Woodruff keys seldom shear and it is mainly the shaft keyway into which the key sits which gives way and usually this is by wearing away the outer edges of the shaft.
 
Thank you for that info - I just assumed that the woodruff key would shear because I can see no other "shearing mechanism" on the bow thruster. Perhaps it doesn't have one?
BTW the bow thruster has continued to function perfectly since I put the boat back in the water in April this year - happy days :-)
 
Assassin said:
Woodruff keys are not roll or shear pins and are not designed to fulfil the function of shearing as they are merely a method of attaching a parallel (or tapered) shaft to another bore of the same shape and transmitting the full power from the shaft to the bore, often with a lot of contingency.

Woodruff keys seldom shear and it is mainly the shaft keyway into which the key sits which gives way and usually this is by wearing away the outer edges of the shaft.
Click to expand...

Then very poor design if the pins that are designed to shear, or are likely to shear, require a boat to be lifted to replace them.

I dont think this is the first time I have heard of this type of thing and, presumably, a bowthruster owner only discovers it the first time it happens.
 
Wikipedia suggests that woodruff keys may be used as shear keys - I am not sufficiently qualified to know whether or not this is true!!
 
A Woodruff key is a shear key, in the sense that it transmits shaft torque by shear stresses across the key. On tapered shafts the interference of the tapers would probably transmit most of the torque, leaving the key to make sure the shaft is locked to the bore. I don't think one would normally be used as a torque limiting device by being designed to fail, as the precise form of the failure would be much harder to predict than that of a shear pin.
 
hey folks, i have a similar problem. my motor is whining and not providing any thrust. i removed the motor and found the coupler was loose, thats one problem. im hesitant to put it all back together as i think there is a bigger problem. i can freely move the key under the red X. i would expect there to be some tension? if so, im gonna keep it apart and troubleshoot the gearbox when out of the water (which i wasn't planning on for another year or two)
Screenshot 2024-06-24 at 10.48.03 AM.jpg
please let me know if you have any thoughts, im having trouble finding a mechanic who will touch this thing. thank you for the support. Screenshot 2024-06-24 at 10.48.12 AM.png
 
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