Aluminium issues

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matsandys

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I'm looking after an aluminium boat. The owner is, shall we say, "relaxed and absent". The electrics look dodgy and the hull is reading a 12v charge. Any advice out there on how I can minimise the damage for now, without engaging a sparky for a week to get to the bottom of the problem.
 
Sounds like a shore power earth fault, has it got the shore supply connected to 12 volt negative, if so it needs a galvanic protector.

Disconnect battery and shore power and take another reading, the marina may have impressed cathodic protection or a boat nearby is leaking 12 volts DC.
 
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I'm looking after an aluminium boat. The owner is, shall we say, "relaxed and absent".

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When you say "looking after", are you being paid, or just doing a favour, or using it in return for looking after?

If the owner is relaxed and absent, I could suggest that you need be no less relaxed?

I'm no sparks but it might help if you tell us what you are connecting your meter to to identify the 12v "charge".

Will the owner foot the bill for a sparks? If so, and you dont really know what you are doing, (in the nicest way /forums/images/graemlins/smile.gif ), perhaps you owe it to him to get professional help before his boat wastes away?

What happens to the reading if you disconnect the shore power?

Cheers

Richard
 
Thanks to all. Will disconnect shore power and check. Maybe best just to have this and batteries connected only when needed .... and disconnect everything overnight
 
If "the hull is registering a 12volt charge" how did you arrive at that? Was it by putting a voltmeter across battery live and hull, in which case expect it if the hull is bonded to the negative ground of battery/engine. If however, you get 12volt between hull and sea-water, not so good!
 
If measuring between battery negative and the hull and seeing 12V you probably have a wire chafed through and shorting on the hull. Usually 12V electrics are fully isolated from the hull on an aluminium boat.

The shorepower is unlikely to be causing this. However, I would advise fitting an isolation transfomer over a galvanic isolator for an aluminium boat.
 
Time to panic and tell the owner to get in an expert IMHO.

Ali can disappear pretty quickly if you really have this amount of Potential Difference in salt water.

Things to look for include ANYTHING COPPER dropped in the bilge and the proximity of steel boats with electrically active hulls. { Whatever that means.}
 
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Time to panic and tell the owner to get in an expert IMHO.

Ali can disappear pretty quickly if you really have this amount of Potential Difference in salt water.

Things to look for include ANYTHING COPPER dropped in the bilge and the proximity of steel boats with electrically active hulls. { Whatever that means.}

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It means the steel boat is a cathode and alloy is now an anode so will fizz away to nothing like all anodes do.

Avagoodweekend......
 
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