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Old 21-05-2010, 11:54   #16
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Originally Posted by biltong View Post
Can anyone or everyone try and explain the process of electrolysis on yachts, especially when surrounded by other boats in a harbour. How will being connected to shore power via a battery charger affect the situation. I thought I knew the answer to this, but the more people I ask, the more answers I get.
Well - I can't help with any answers but co-incidentally, I picked up a boat which had just been splashed, in Mobile, for onward delivery to BVI. Did all the pre-voyage checks etc but by the time I got to USVI, this had happened.

Initially, I thought the yard where a lot of work, including stainless, had been done, had used "Ace Hardware" screws instead of marine grade SS but then, due to numerous annoying electrical problems en route, I began to think electrolysis.

Sure enough, when my favourite electric guys in Tortola ran the meter over it, the boat was producing a stray current. Well - that bit's easy....its finding the casuse which can take time. Luckily we found it on the first go - a bad bow light wire which had not been helped by the amount of green stuff we'd taken over the bows on the long beat down.

So - if you think you've got an electrolysis problem - get on it asap!!
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Old 21-05-2010, 12:07   #17
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In a nutshell, an isolation transformer stops stray direct current between your boat and the marinas electrical system.

It stops your boat from becoming its sacrificial anode via your shore power cable. You can still get electrolysis from other sources though.


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Old 21-05-2010, 12:27   #18
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Don't forget here that your whole boat (inside and out ) is wet or at least damp enough, with SALT water. Any amount of insulation is pretty well ineffective as the coating of this dampness on fibreglass, across rubber/plastic/wood makes for an electrical connection, between everything, sufficient to give you electrolysis nightmares.
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Old 21-05-2010, 14:41   #19
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Multimeter probe into bilge water...

I got a reading of +.04V when I stuck a multimeter probe into my bilge water.

Lifting the switch and pump out of the "sump' and keeping the bilge dry has (hopefully) greatly reduced the problem.
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Old 22-05-2010, 00:41   #20
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Thank you to everyone who responded to my thread. Though more informed and educated than before on this subject, I am more confused than ever. I think I will be using a wooden engine, through hull fittings and prop from now on. And if that doesn't work, I am going to start using wooden batteries too.
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Old 22-05-2010, 09:23   #21
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Do be careful when using wood! Electrolysis and attempts to protect it on wodden hulls can cause severe rot problems!!
Yes, true..

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