Stray current

Redboat42

Recruit
Joined
Mar 17, 2015
Messages
3
Last haulout my zincs were gone and lead keel had pushed off paint a along with epoxy bottom. I had lost two raw water pumps before it finally hit me. I checked with a good quality multimeter and read 6.5 amps when going from a known ground and touching other probe to raw water pump. The only thing I have changed is adding a new radar. It is freaking me out. I installed a new zinc saver on the shore power neutral but dont know how to best isolate the issue. Any ideas would be greatly appreciated.
Randy
 

DeepCMark58A

Commander
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Aug 17, 2015
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2,030
Is this in a marina or private? If it is in a marina it is possible that it could be another boat or from the shore power. There is a reason why marinas do not allow swimming or diving.
 

Redboat42

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Joined
Mar 17, 2015
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3
That is certainly one reason not to swim. The marina manager claims they recently tested power and water around boats and all was good. I got new shore power cord and zinc saver. I could remove engine ground perhaps and see if block remains hot ?

Perhaps a ground break switch in ground cable? They are only $30;or so. I don't know what else to do. Hiring a elect is not really an option I can afford.
 

DeepCMark58A

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Aug 17, 2015
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2,030
Do the shore power outlets have a GFCI? Yeah and a ground testing meter is over $1000.
 
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Thalasso

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Joined
Jan 18, 2011
Messages
2,876
GFCIs offer almost no protection from stray current, because corrosion begins at a much lower currents levels than required to trip a GFCI
Generally there are two diff. corrosion on boats
Galvanic which is a long subject then there is electrolysis.(leaking power from shore power)

You said you recently added radar. There is a possibility you have leaking DC power causing it.
I'd check the ground for dc currents first.
Here is a great article from Fluke:
http://assets.fluke.com/appnotes/ele...r/B0269b_u.pdf

Use a clamp on meter on your shore power cord. It should read 0
Test the marina's ground lead. Should be 0. If there is any voltage start by unplugging one by one other boats on that circuit. This should tell you if another boat has a wiring problem that's causing your problem
 
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Grandad

Lieutenant Commander
Joined
Jun 7, 2011
Messages
1,504
Last haulout my zincs were gone and lead keel had pushed off paint a along with epoxy bottom. I had lost two raw water pumps before it finally hit me. I checked with a good quality multimeter and read 6.5 amps when going from a known ground and touching other probe to raw water pump. The only thing I have changed is adding a new radar. It is freaking me out. I installed a new zinc saver on the shore power neutral but dont know how to best isolate the issue. Any ideas would be greatly appreciated.
Randy

What would freak me out the most would be seeing an ammeter showing 6.5 amps of current flow. What voltage can you read between the raw water pump and ground? That kind of current can only be from a very solid short circuit. Just for perspective, consider that 6.5 amps is 6500 milliamps, compared to the maximum allowable trip current on a GFCI is only 5 milliamps. - Grandad
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
I have to say 6.5 AMPS is amazing to read. I wouldn't set foot near that place until the electricity is cut off and the problem was located and fixed. Here in Georgia there was an electrocution this year from stray power in the water and a young girl jumped in to go swimming and got electrocuted and died. So be extremely careful. It doesn't happen to the other guy all the time. JMHO
 
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