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Old 14-11-2010, 21:51   #1
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Electrical Problem Corroding Massive Holes into Anchor !

We fitted a large bugle anchor to my mates Duncanson 35 before our trip to Brisbane from Adelaide. We are half way now. I'm not sure the boat had seen much rough weather for a long time, but in short the anchor well filled up to the level of the internal hatch spilling muddy water into my bed. To my surprise I could not find a drain hole!

Now the whole windlass has a green corrosion look to it and when you touch it or the bow railing you get a tingle from the batteries. I think it got salt water splashed all over the internals when the anchor well filled up. Where the anchor touches the anchor roller the stainless fitting almost melted a hole through the anchor from electrolysis in one week.

I took a look at the wiring and it appears they have run 12V+ straight to the winch then the foot switch is joined on the cable which joins the earth strap (which runs through the bilge essentially joining the negative terminal of the batteries to sea water). I'm not sure if this is the way its usually done. I have disconnected the positive cable for now.

The way it is, the windlass always has a positive at the motor, and the negative is made when you hit the foot switch, but the chain also has reference to negative as it is sitting on a uninsulated copper earth strap. So I think the salt water or other prob as allowing some current to flow from the constant positive through the earthed chain or bow roller etc. Anyhow I was thinking of connecting the negative straight up to the winch and fitting the switch to the positive so that the winch does not have a positive reference until you hit the foot switch?

Good or bad idea?
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Old 14-11-2010, 21:56   #2
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That's the usual way to do it.
Negative connected all the time and switch the positive, either directly or with a solenoid.
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Old 14-11-2010, 22:57   #3
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Cheers. I already swapped it over. Seems to have fixed the prob. I was just wondering if anyone had any ideas why it might have been like that? Or what about a uninsulated earth strap for terminating all negatives to? Seems like a way to invite electrical probs running an uninsulated earth strap in a salt water environment. Seems what works on cars might not be the best for boats.
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Old 14-11-2010, 23:28   #4
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No harm with an uninsulated negative so long as corrosion is not eating it away, especially at the terminals. I would be cautious and coat the terminals with something so you get a good return path. I use Tef-Gel or silicon grease if it's any sort of petroleum based rubber. Both resist water from causing corrosion.
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Old 15-11-2010, 01:28   #5
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There is no corrosion on the terminals. Just all around the area with the stray current. A bare earth referenced to sea water and metal parts of the boat just seems to double the chance of fault like this. Not to mention damage if hit by lightning? If it was insulated the whole railing chain and bow roller wouldn't serve as a return path. Its not the way I would wire a boat. I would go the other way with double pole switching, but thats going to be a PITA in reality.
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Old 16-11-2010, 07:45   #6
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when i wired up my windlass i did the normal and just fitted the solonoids in the anchor locker and the coroded in around 3 to 6 months so in the end i got fed up with having to keep replacing them and cleaning them so i fitted all the connections into a lock lock box (like Tupperware but with locking sides) which is airtight and since then i have not had any problems with corrosion, the boxes only cost a few $ and work great as long as they are not in direct sunlight as then they go hard and crack. this was a cheep way of fixing a problem most people have it has been good now for around 5 years and never killed the solenoids since.
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Old 16-11-2010, 13:40   #7
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Quote:
That's the usual way to do it.
Senor: Didn't you mean "That's not the usual way to do it"?

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Old 16-11-2010, 20:09   #8
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Quote:
Originally Posted by CharlieJ View Post
Senor: Didn't you mean "That's not the usual way to do it"?

Charlie
I was responding to the original poster who said he was thinking of wiring the switch in the positive lead.
In my post, I meant the normal way to do it is to switch the POSITIVE lead.
Negative can stay connected. I think that's what I said.

(Typing in the dark on a laptop running on my boat's long distance wifi because due to a big windstorm last night, we have had no power for almost 24 hours)

Steve
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Old 19-11-2010, 00:07   #9
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hmm time to repeat something here:

1. a good windlass has an insulated negative. This means that the metal parts are not connected to DC ground. You can often check this easiest at the negative terminal on the motor... it should have visible insulation between it and the motor-housing, just like the positive terminals.

2. a windlass must never be connected to a ground/bonding system... nor should any metal part touched by chain while at anchor (like metal bowroller).

The reason is that there is a potential difference between metal grounding plates and the anchor buried in the seabed. The water between the anchor(chain) and grounding plate(s) completes the circuit.

When every boat would have these 2 points covered, only half the amount of anchor chain would be sold

cheers,
Nick.
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