Bow thruster Nobles 4hp 12v

[blampied]

Hi
I have a 1996 33' single engine Aquastar boat with an original fit 4hp Nobles 12v bow thruster.
The thruster is working fine to port.
It also works to Starboard, But anything more than a few second use and it has serious overheating issues.
Ends up melting the spring washer under the contactor bolt.
I'm assuming it has a short circuit somewhere?

I'm currently living aboard the boat travelling along the Spanish/French Med coasts, so don't want to have the boat lifted out if possible, what are my options?

Am I missing anything obvious that I should check?

Can the motor be removed for servicing with the boat in the water. Is the drive sealed to the tunnel and therefor the motor be unbolted from the drive and lifted off without danger of water getting into the boat?

Is the motor likely to be serviceable, assuming I can find a marine electrician.
And would a motor of this age be worth servicing?

If the motor is U/S is there likely to be a replacement motor still made that fits directly onto the drive unit? Or has everything moved on since 1996

If I ended up having to replace the bow thruster (200mm tunel) are bow thrusters makes all comparable, would another make fit directly into the tunnel, using the existing mounting holes, or would the tunnel need to be cut out and replaced as well?

It looks like AquaFax were the UK importers at the time of installation but no longer import them. Nobles appear to be Dutch and their website is in Dutch,
Can't understand most of it or see anything that's likely to be useful.

Any advice great fully received

 

[pvb]

Nobels thrusters are listed by Sigma Supplies, might be worth a phone call to them - http://www.sigmasupplies.co.uk/index.html

 

[duncan99210]

If your thruster controls are similar to those of an anchor winch: that is a low current control circuit which connects to a control box with two relays in it, one for port, one for starboard, then I'd look at the control box rather than the motor. It sounds to me as if the starboard relay is failing to make a proper connection, causing poor power delivery to the motor and overheating the control box.

 

[pvb]

It also works to Starboard, But anything more than a few second use and it has serious overheating issues.
Ends up melting the spring washer under the contactor bolt.
I'm assuming it has a short circuit somewhere?

Reading this again, I'm wondering. Presumably there's a fuse or a breaker in the thruster circuit? If so, it's unlikely that there's a short circuit, otherwise the fuse/breaker would blow.

I'm not a fan of spring washers on high-current connections. Have you tried getting rid of the spring washer and just tightening the connection? Does the port circuit connection also include a spring washer?

 

[blampied]

Hi On further investigation it looks like the motor and drive unit are one, so probably can't remove the motor without flooding the boat.
With this being original fit when boat was built I would have expected the thruster to be fused, Im the third owner of the boat and have had the boat two years. I have never seen a fuse for it and looking again I have not managed to locate a fuse. So I am now assuming the thruster is not fused. As far as I can tell there is also no warning buzzer for overheating.

With the plastic guard removed, ( it also has some evidence of melting)
Having wife activate the thruster to starboard for two seconds at a time then putting my finger on the contactor plate, after the first two second blast it's only just starting to warm, after a second two second blast it's getting quite hot from the centre of the motor where the drive shaft would be along the contactor plate the heat travelling rapidly in the direction of the contactor bolt with washer. On third two second blast the plate gets too hot to keep finger on and a small whiff of smoke rises. Still not hot enough yet to melt the washer but getting very hot.
Acctvating the thruster in the other direction for those short durations doesn't cause a noticeable temperature rise.

I'm unsure if I can put pictures on this site, (My FaceBook page is under Paul Blampied, I don't know if you have FaceBook but I will put the pictures I have taken on FaceBook just in case you have and want to look)
I have now sent (thanks to pvb suggestion )an e.mail to Sigma asking for advise.

 

[blampied]

Hi Duncan
Thank you for that.
I'm not aware of a control box, the power cables from the battery just go direct towhat I assume are relays on the side of the motor. Then there is thin cabling going to the joystick control.

I don't think I can put photos on here? If you have FaceBook I have put some photos on my faceBook page 'Paul Blampied'
Thank you.

 

[duncan99210]

Looking at your pics on FB, the rectangular box next to the motor contains two relays which deliver power to the motor in response to your using the port/starboard controls (that what the light weight wires from the control are for). Again from the photos, one of those relay coils would appear to be overheating, which is causing your problem. It should be easy enough to replace the relay box with a new one which should solve your problem. I don't think there's anything wrong with the motor. If it runs in one direction, it should be fine going the other way.
If you were to replace the relay box, you might have to place it slightly away from the motor, rather than using the solid metal plates you currently have to make the connections. If that is the case, make sure you use thick enough cables for the job with properly crimped on terminals.

 

[blampied]

Thank you everyone for your help.(pvb and Duncan)
I have removed the spring washer, however it made no difference still overheated
I have checked the earths and fitted an additional earth cable, also made no difference.
I have e mailed Aquafax the original supplier of Nobels bowthruster in 1996, reply we no longer deal with Nobles
I have e.mailes Sigma, waiting for a reply
I conclude that Duncan 99210 is correct and it is the starboard relay that is overheating/dying
I will attempt to source a replacement relay and try not to use the Stabourd direction thruster
(Rather difficult as we expect to spend the summer on the Canal Du Midi)
I have also fitted spacers under the cover mounting bolts to allow more cooling airflow.

 

[Mrnotming]

Using a multimeter in the 0-20v range check the current drop on each relay when in operation.This should give you a value which if the same in each instance,could indicate that the current available is less than required to hold the relay properly shut.Some of the relays need the engine running as well as stored battery power to ensure operation.If the unit was ever operated when the ships batteries were bad or low,burning of the contactor contacts and or shorting of the coil might occur and produce your burning symptoms.Fires have been known to result from undercurrent conditions where the relays are unable to remain closed and start an arc.Especially in one case where sails were stored nearby.If the current is not maintained in operation,it may need a replacement supply battery,if fitted already,or the addition of a more local battery to prevent current drop.Other than that,one presumes that the boat's manufacturer designed the system to function properly,or is the unit an add on later?