Bow Thruster issue

I have a sidepower bow thruster. I recently noticed it is unusually quiet. So much so I can barely hear on the bridge with the engine running. It also is suddenly less effective than it used to be. I'm not sure where to start with something like this. I won't be hauling the boat until Columbus day.

I'm hoping someone has seen similar behavior and has an idea where to begin troubleshooting.

lost the prop

I don't have a bowthruster and never used one, but having worked on pumps for years I would say you may have lost a propeller. Or you sheared off a shaft pin or gear making the prop shaft idle.

Try it tied to a dock with engines off. Both directions.
Are you getting any thrust at all? If none, could be a broken shear pin, prop hub, or no prop at all.
Some thrust could be low voltage to the motor, worn out brushes, heavy barnacle buildup or slipping prop.
Beyond that, check the troubleshooting section of your manual.

Put a voltmeter on batt terminals (or on motor terminals) and monitor while a helper runs the thruster. On my 12V unit, batt reads about 10.5V with unit running with healthy batt.
Below 10V, it means weak batt. If it is like 8V, unit barely makes thrust at all.

Get in the water and spin the blades (if they're still there). You'll feel the gearcase resistance assuming you haven't sheared a pin. When mine stopped thrusting last year is was do to 80% blockage of the tunnel from Barnacle build-up..

My first thought is have a diver check it out. However, I'm in cold water. If you are in warm water you may feel comfortable checking it yourself.

Well they've now gone from 'quiet and less effective' to 'Not Working'. They were working before, just noticably quiet and much less effective. Now, the only thing I hear is the 'click' of the solenoid when I hit the thruster left or right.

If the prop were missing, I'd have no reaction at all, but that wasn't my initial symptom. I'd expect to at least hear the motor spinning. Batteries are fine for all other uses, including Windlass.

I suspect there is an issue with corrosion in the connections. I'm going to have to start tearing thing apart the main berth to see if I can find it.

If you're not hearing the motor run, and you hear both solenoids (there are two, one for each direction) click, I would start with the motor brushes. They're relatively easy to get to and pull out. They may be worn down or they may be bound up in the brush holders. As the brushes wear, they have to move forward to maintain contact with the armature. Sometimes they can get bound up with particles worn off the brush itself. It's also possible that the brushes are just worn out and need to be replaced.

Ted

This one has taken me a bit to get to the bottom of, but I wanted to circle back around.

(much earlier in the thread I see I was talking in the plural, which I don't understand why because there is only one.).

I went through the rest of the season with no thruster, which was fine as it allowed me to hone my docking skills and significantly reduce my dependence on it. When I hauled the prop was in place and there was no growth or obstruction. Spinning the prop, you can 'feel' the differential turning in the pod.

I removed the bow thruster, realizing I could have done that in the water. The shear pin was intact.

There was a significant amount of carbon dust built up on the inside. I used an air compressor to blow out all of the carbon dust. This model has 4 brushes.

Two of the brushes had a significant amount of meat on them. They do not appear to freely move in the brush guides. The other two are so worn, that the springs are resting on the edge of the brush guides and can no longer push those two brushes down any longer.

judging by the difference in size, it appears that two of the brushes seized in the brush guides quite some time ago. The remaining two brushes are simply too worn and can't be pushed by the springs any longer.

I ordered a set of 4 brushes from Imtra. This looks like it will be an easy solution.

Thanks for the update. Often you never hear when the root cause is found. I have these thrusters too so I will tuck it in my knowledge bank. If you dont have spare shear pins suggest you buya few. I pay about $3 and it is a 30 minute fix that can be done easily and really save the day.

Hi,

https://www.imtra.com/Collateral/Documents/English-US/Products/SP_Troubleshooting_Guide_with_IPC.pdf

Maybe this guide help you...

NBs

North Baltic sea said:

Hi,

https://www.imtra.com/Collateral/Documents/English-US/Products/SP_Troubleshooting_Guide_with_IPC.pdf

Maybe this guide help you...

NBs

Click to expand...

A great resource for troubleshooting, thanks. Here is the doc I was following:

https://www.imtra.com/Collateral/Documents/English-US/Products/Guide_for_checking_motor_brushes.pdf

I got my new brushes in and I'm amazed at how far gone two of my brushes were when able to compare with new ones.

I started cleaning the commutator prior to replacing the brushes. As I got into it, I noticed that one side of the commutator is fine. However, the other side has a groove/trench ground into the commutator where the brushes are rubbing.

This is only on one side, which leaves me to suspect that the 'rotor shaft' (??) is not properly aligned.

I'd hoping that someone is going to say "Clean up the Commutator, clean the grooves in the commutator, replace the brushes and move on.

I'm afraid to hear "You're going to need to rebuild/replace the entire thing."

Any thoughts would be greatly appreciated.