Bow thruster sparking & carbon dust

[trialframe]

On our Nordhavn 43 we have 12v Side Power bow and stern thrusters which are both working well. When checking the bow thruster compartment recently there was a thick layer of carbon dust on everything. Previously (for 5 years) it has been very clean in there. On observation of the motor running there is a lot of sparking at the brushes & fine carbon dust can be seen in the air.
The stern thruster motor gives almost no sparking or dust.
I checked the voltage under load and it is 11.6v which is well within spec.
I removed the motor and cleaned the armature with fine aluminium oxide paper. I also cleaned between the segments and checked that they are undercut - yes they are. I replaced the brushes with a new genuine set.
Unfortunately after all this there is no improvement.
Any ideas??

 

[Seastoke]

Was the com worn or have grooves , it sounds like it needs taking to a motor rewind firm and they will rebuild the com and bed in the brushes , then you can forget it .

 

[Momac]

Is there a solenoid and could the soot be from that due to the contacts burning?

 

[trialframe]

There is a solenoid but the dust is definitely from the carbon brushes.
Could a fault in the motor windings cause this?

 

[trialframe]

Does anyone have a recommendation for an electric motor repair facility in Hampshire or Dorset?

 

[petem]

I've got a couple of sidepower bowthruster repair guides. Send me your email address and I'll send them to you.

 

[Portofino]

Have you checked the battery connections / wiring connections to this bow motor .Even though the V appear ok a weak current might help spark that would otherwise not happen like @ the stern motor .

 

[trialframe]

The motor is right next to the bow battery which is a 210 ah lifeline agm. I have checked the connections which appear to be good.
Maybe I need to source a clamp on meter to measure the current which should be in the order of 700 amps.

 

[Solent Sailor]

I have my Sidepower in with a very good (so it appears so far!) company at the moment. I can let you know how it goes. Osmotech use them for all of their electric motor work and rewinds, which is a good testimonial - and its a lot cheaper than going via the middle man.

 

[trialframe]

Thanks Solent Sailor - it would be good to know for the future.
There has been a happy ending to my problem.
I took the motor to a small business called Borg EMR near Ferndown. Nick Borg stripped my motor, replaced the bearings (one was shot) and skimmed the commutator etc. Result - it's back to normal at a very reasonable cost & all done within one day.