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robe54
robe54

Posted: Sun May 01, 2011 11:26am

Post Subject: Vetus Bowthruster

Help Please I own a 2009 57' narrowboat which I purchased in December 10. I have recently started having problems with my Vetus 55kgf bowthruster blowing the 250 amp fuse between the main switch and bettery , I can not see any obvious wiring damage, the thruster shaft is turning with minimal 1 handed effort. With the main battery switch in the off position the battery is registering 12.7 volts. The boat was stood out of the water at the brokerage over the winter until we purchased it. No problems were encountered when initially testing the thruster and on our "32 mile transit trip" to the boats new home. But have started having problems since then. When putting the last fuse in I tried the thruster giving a short burst either way for about 5 seconds after which time the link in the fuse was showing signs of failing. So I have not used the thruster since. Any advice on where to start looking for the faiult would be appreciated.

Tony-B
Tony-B

Posted: Sun May 01, 2011 1:19pm

Post Subject: Vetus Bowthruster

I think we need to know more about how your boat is wired. Is this fuse the main fuse protecting the main domestic supply cable from the domestic battery bank or is it on supply to the thruster from the bow-thruster battery? Any motor creates a surge current as it starts so may require a slow blow fuse. Are you sure your replacement fuse is the same as the one specified by Vetus? Whenever a motor is prevented from reaching its design speed it will draw a higher than designed current. The slower it spins the higher the current so my first thoughts must be to do with something slowing the motor like a fouled prop or a partial seizure. Once you are sure that is not the problem I would be looking for a partial short circuit in the motor. Check the commutator (if you know what one is) and ensure all the little bars look the same. If one or more appear burnt or flattened you probably have a faulty motor. Also do what you can to clean as much brush dust out of the motor as you can. This is conductive and may be causing a short circuit. Tony Brooks

robe54
robe54

Posted: Sun May 01, 2011 3:38pm

Post Subject: Vetus Bowthruster

The problem is with the slow blow fuse between the thruster motor and thruster battery. The fuse rating is 250 amp the same as the original one taken out when the problem first came to light and is the same rating as per Vetus manual. I am not sure if the thruster shaft should spin easily and freely when turned by hand, I can turn the shaft with one hand but there is slight resistance. Rob Eddon

Tony-B
Tony-B

Posted: Sun May 01, 2011 5:26pm

Post Subject: Vetus Bowthruster

I think the motors are directly coupled to the prop so it has to drive through some kind of bevel gearbox or other drive arrangement so given that, plus the resistance of the water against the prop and the friction of the brushes against the commutator there will be some resistance. The problem is that there is no way of telling us how much there is over the internet. Have you checked the commutator and cleaned the brush dust out of the motor yet? If so then it may well be a case of getting an engineer in. Have you given it several turns in both directions? It might be something winidng around the prop in one direction and unwinding in the other. Tony Brooks

robe54
robe54

Posted: Mon May 02, 2011 11:33am

Post Subject: Vetus Bowthruster

Hi Tony Thank you for your responses, I am currently offshore Norway working but will look into the issues you have suggested once back over at the boat in a couple of weeks time. Once the problem has been resolved I'll post again to let you know of the outcome. Rob

robe54
robe54

Posted: Thu May 19, 2011 7:33pm

Post Subject: Vetus Bowthruster

Hello Tony An update on the bowthruster issue. I have done some further investigation, the motor brushes and commutator are in as new condition, all the connections have been checked, cleaned and retightened, with no obvious problem identified. However, I did come across another issue of the shower discharge pump with a slack discharge pipe connection which was subsequently discharging 50% of the shower water onto the deck under the cupboard every time the shower was used. The bow thruster cables run through this space and were found to be "damp" to say the least. I have dried out the floor and the cables then tested the thruster in both directions with the "slow" blow fuse remaining intact. Would I be correct in thinking the damp cables would cause excess current and subsequent fuse blow as every thing else is appears in as new condition.

Tony-B
Tony-B

Posted: Thu May 19, 2011 9:17pm

Post Subject: Vetus Bowthruster

The only way I can see the damp cables having that much effect is if the insulation is damaged so the current shorts through the damp to the hull. If the cable is plastic coated I can not see even long runs with the cables touching would cause the problem. however it seems it did. I must point out that the BSS is likely to be highly unimpressed with cables run so low in a boat. All cables (apart from bilge and possibly shower pump cables should be run above the level of possible bilge water. I am happy that you seems to have solved it. Tony Brooks

benkson68
benkson68

Posted: Wed Sep 09, 2015 11:35pm

Post Subject: Vetus Bowthruster

I too have had a blown fuse, but looking at the specification for the bow thruster it takes a maximum of 375 amps. I assume this current is taken when starting the motor, hence the 250 Amp fuse MUST be a slow blow type otherwise it would blow very quickly. Mine blew when I used the thruster over several minutes with short pulses. Local chandlery had 250 Amp fuses in stock but these are NOT slow blow - you must get the actual Vetus replacement to be absolutely sure. Fuse replaced with correct type, slap on wrist for using bow thruster too frequently in short bursts, all now working fine. I've heard of several people having repeated blown fuses, so this may be a common problem.

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