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Old 21-03-2010, 17:40   #16
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See post #3. Disconnect the boat from the shorepower. Measure voltage or current to ground from your shorepower ground wire to seawater. Do the same for the marina ground wire.

50/50 chance you can smugly tell the marina to get busy with their tools....
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Old 21-03-2010, 18:56   #17
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Originally Posted by denmanislander View Post
Should I start a new thread or will you guys check in on me later this week?

We'll check in...Im seriously interested as my Sea Ray got ate up a couple years ago and I could not figure it out either..I always believed it was not my boats doing....this is a good education for more then just yourself...Thanks for posting about it!
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Old 21-03-2010, 19:01   #18
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And do get it fixed. I do not want to get bzzzzzed when I go diving on my zinks ever again ;-)))

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Old 21-03-2010, 19:07   #19
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Ok shameless plug but if you read my article on testing your shore power you should be able to locate the problem. If you follow all these tests and cannot find the problem I would like to know so I can learn something.
http://www.projectboatzen.com/forum/...e-Power-System
Good luck
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Old 21-03-2010, 19:38   #20
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And that was supposed be simple?

And people think diesels are complicated..
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Old 22-03-2010, 01:00   #21
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Yes, I think you truly found a source of free energy ;-) I would also like to know how the marina determined you are back feeding two amps.

You can test your installation but as you didn't pull out your fluke immediately, you might not have all the tools needed to do this like Wayne describes. I also have the feeling that the marina isn't waiting for you to tell them the problem is on their end.... which brings me back to my original suggestion of letting them fix their own problems while you spend your time, effort and money to make sure you are okay and safe and not being pointed at by anyone supplying you shore power (= install isolation transformer by qualified installer who also checks your AC installation).

cheers,
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Old 22-03-2010, 05:58   #22
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I agree with Nick that an isolation transformer is the way to go but you still need to be sure you're boats electrical system is correct or you will still have a safety hazard on board. It sounds to me like you have a neutral ground connection somewhere on board, I would look at this first. A simple VOM can tell you a lot and you really should have one in your took kit. I have found over the years that 9 out of ten owners blame the dock or the boat next to them but 9 out ten times I find the problem on the boat that is having the problem not the dock or the boat next to them, but then again you can never assume anything. Careful methodical testing is the only way to get to the root of the problem. Start at the source (dock power) and work your way thru. You can speculate and guess all day long but till you get the meter out you are not going to fix it.

Good luck
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Old 22-03-2010, 15:04   #23
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THis is a marina problem, with no source power its has to be them .... unless The water around you is live......
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Old 22-03-2010, 15:33   #24
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Professional BoatBuilder Digital Issues

Scroll down to the April/May 2006 issue. It has a great article about testing your AC system.
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Old 22-03-2010, 16:49   #25
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I agree with daddle in Post #16 but only for potential.

Disconnect your shore power cord from the pedestal. Put one DMM probe in the ground position on the pedestal and place the other probe in the water. Record the VAC reading. Anything above a few mVAC is excessive and must be corrected.

With the shore power cord still disconnected from the pedestal, put one DMM probe on the ground spade of your cord and the other probe in the water. With no power source in operation on your boat, this should give a 0 mVAC reading.

To check for proper ground to neutral isolation on your boat, set your DMM to read resistance, go behind the panel and put one probe on the neutral bus, and the other on the safety ground bus. As Wayne referenced, you must have a reading > 25,000 ohms.

Let us know what you find.
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Old 22-03-2010, 21:59   #26
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I would repeat the first two voltage readings CharlieJ mentions for DC too. You actually have to add the two readings because AC will be superimposed on the DC offset (and I have seen crazy DC levels too)

cheers,
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Old 22-03-2010, 22:10   #27
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Here is the procedure for determining whether DC (galvanic or stray) is flowing through the safety green wire onto or off of the boat:

1. Unplug the shore power cord at the pedestal.
2. Put the black probe from your DMM into the ground slot in the pedestal.
3. Put the red probe from your DMM on the ground prong on the disconnected shore power cord.
4. With the DMM on Volts-DC read the voltage and note if there is a negative sign before the reading. If there is a negative sign showing, reverse the leads. If there is no negative sign, proceed.
5. Now here is the tricky part: Electrons do not flow from positive to negative (red to black) as we are accustomed to and we are interested in electron flow here.
** If the red probe is on the boat side and the black probe is on the shore side and you are getting a positive reading, then current is flowing onto your boat from the shore side.
** If the red probe is on the shore side and the black probe is on the boat side and you are getting a positive reading, then the current is leaving your boat.


Hope this helps.
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Old 22-03-2010, 22:25   #28
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Here is the procedure for determining whether DC (galvanic or stray) is flowing through the safety green wire onto or off of the boat:
Technically true. But not diagnostic. Your procedure does identify the direction but not the culprit. The culprit has an (improper, illegal, unwanted) voltage relative to ground that causes a current to flow. That electrons of that current might flow either way.

The OP does not even need a meter probably. Put the boathook well into the seawater and see which side's ground arcs to it. It doesn't seem like we're dealing with some small potential here. This step should be so simple.
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Old 23-03-2010, 05:26   #29
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Just a thought: Can you plug a standard 3-pin "household" power cord into the dock power box? If so, there are inexpensive $5 socket testers sold in most hardware stores. Plug it in, read 3 LEDs against the label, and it will show up most common faults.

If you can only plug in "marine" plugs, it may still pay to use one of these with a plug adapter if you can reasonably make one up. Easier to convince the marina it is their problem (if it is) than asking them to believe in meter results they may not understand.
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Old 23-03-2010, 06:22   #30
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Technically true. But not diagnostic. Your procedure does identify the direction but not the culprit.
Excuse me...it is very diagnostic and used every day by qualified marine electricians to determine if a galvanic/stray current is flowing on or off the vessel thus isolating the problem to the shore or the vessel.

The OP's description of an "arc" certainly implies that this issue is not galvanic/stray current in nature which is why in #25 I provided a procedure for determining the potential on the safety ground wire with respect to the water.

I consider sticking a boat hook in the water and watching which way the arc jumps to be "not diagnostic" and potentially dangerous.

Charlie
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