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Old 10-03-2014, 07:48 AM   #1
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Grounding or bonding issue???

On haul out yesterday it was apparent that my prop, rudder and metal rudder bracket were thickly coated in a hard scale. None of the other boats hauled today at our marina had this. It was very easily dissolved with a light muriatic acid solution but obviously I have an electrical issue. There does not seen to be any corrosion on these parts but something is wrong and I want to correct it. We are in fresh water but this likely doesn't matter. Where do I start?? Any suggestions would be very much appreciated.
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Old 10-03-2014, 11:42 AM   #2
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I have just my sterngear bonded to a single zinc plate on the transom and a Drivesaver to isolate it from the engine. Never had a problem in 20+ years. BUT, always heavy barnicle growth on the metal skeg bar by the end of the year, right over the bottom paint. Last year I decided to change that and was told by Pettit that applying copper base bottom paint over even primed metal neutralizes the paint right away. They said a barrier coat or non-copper paint was needed for metal. This spring I coated my skegbar with two coats of epoxy (2nd thickened) and this year not a single barnicle on it. They were right.

We don't know if your boat is moored or has dockside power or if your changed anything this year.
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Old 10-03-2014, 12:13 PM   #3
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I believe the OP has a fresh water boat.
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Old 10-03-2014, 03:45 PM   #4
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I'd consider getting a corrosion analysis performed by a competent technician who utilizes a silver/silver-chloride (Ag/AgCl) reference electrode. We had one done last summer and it took about one hour. Money well spent. Here's a link that may help.

Corrosion Reference Electrode Product Specifications
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Old 10-03-2014, 04:28 PM   #5
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Yes I am in fresh water, no barnicles here. I am on shore power in the marina except when out on the water as my refrigerator is 12V and the battery charger needs to keep topping up the batteries. I haven't changed anything significant, new chartplotter and VHF. Did add a bow thruster as well and funnily enough no coating on it at the bow of the boat. Larry, I will see if someone in this area does this type of analysis, seems reasonable. Thanks all.
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Old 10-03-2014, 04:48 PM   #6
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Quick Check

Quote:
Originally Posted by LaBomba View Post
Yes I am in fresh water, no barnicles here. I am on shore power in the marina except when out on the water as my refrigerator is 12V and the battery charger needs to keep topping up the batteries. I haven't changed anything significant, new chartplotter and VHF. Did add a bow thruster as well and funnily enough no coating on it at the bow of the boat. Larry, I will see if someone in this area does this type of analysis, seems reasonable. Thanks all.
When you are plugged into your shore power, with a clamp type ammeter check your shore power cord for current flow. Simply clamp around your shore power cord while it's plugged into to the boat. Any current indicates leakage to ground through something on your boat. Any current flow is a dangerous condition in fresh water.
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Old 10-03-2014, 05:08 PM   #7
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Scary, thanks I will try that, I have a clamp type digital amprobe. I assume I need to shut off all boat powered equipment, battery chargers etc. to do this test?
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Old 10-03-2014, 05:19 PM   #8
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Scary, thanks I will try that, I have a clamp type digital amprobe. I assume I need to shut off all boat powered equipment, battery chargers etc. to do this test?
No actually turn everything on...the check is to see that all equipment using power is returning it out the neutral back to source ground rather than out through the bottom of the boat....thus the "zero" reading signifying all is "good".
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Old 10-03-2014, 05:22 PM   #9
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Greetings,
Mr. ps. OK, ya got me. Everything on? What about something that cycles like your fridge? THAT alone will cause fluctuating/different readings will it not and I suspect we're talking milli amps here. Would have to be a damn sensitive instrument I would think.
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Old 10-03-2014, 05:36 PM   #10
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Greetings,
Mr. ps. OK, ya got me. Everything on? What about something that cycles like your fridge? THAT alone will cause fluctuating/different readings will it not and I suspect we're talking milli amps here. Would have to be a damn sensitive instrument I would think.

Not really you are checking the power coming in through the cord cancels out the power going out and if not zero...then it's leaving via the water...

http://assets.bluesea.com/files/reso...lamp_meter.pdf

Check for current leakage. When clamped around cables which include both the hot and neutral wires, there should be no
current reading. If a significant current reading exists, it indicates a fault condition. Using the clamp feature around a shore
power cord can reveal potentially deadly AC current leakage into the water surrounding the boat.
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Old 10-03-2014, 06:07 PM   #11
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Greetings,
Mr. ps. Thanks but still doesn't make sense to me. If everything is off and there's still a power flow THEN you have a leak. If everything is on and cycling, power is flowing but some is doing mechanical work and some is given off as heat/light etc. How do you know how much, if any is leaking?
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Old 10-03-2014, 06:10 PM   #12
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Greetings,
Mr. ps. Thanks but still doesn't make sense to me. If everything is off and there's still a power flow THEN you have a leak. If everything is on and cycling, power is flowing but some is doing mechanical work and some is given off as heat/light etc. How do you know how much, if any is leaking?
whatever it reads is what you are leaking....you may be locked into DC thinking...with AC this test is the recommended one...very basic but a start...

try this for explanation...

https://www.bluesea.com/resources/1381
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Old 10-03-2014, 06:19 PM   #13
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Greetings,
Mr. ps. OK, gotcha BUT you would only be able to detect leakage IF there was an ELCI or a GFCI on board-correct?
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Old 10-03-2014, 06:22 PM   #14
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Greetings,
Mr. ps. OK, gotcha BUT you would only be able to detect leakage IF there was an ELCI or a GFCI on board-correct?
No I don't think so...IF you had a ELCI...it would trip if you had leakage..the reason they exist.

If you DON'T have one...and you get a reading on your power cord...you have an issue that needs correction.

You won't get a reading if you have a fault that is leaking back out the green wire...so that one thing this test doesn't get I think....the test is more for leakage into the water.
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Old 10-03-2014, 06:36 PM   #15
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Greetings,
Mr. ps. I never was very good at electricity. I'm stumped if there are more than 2 wires. Thanks.
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Old 10-03-2014, 09:11 PM   #16
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Let me give it a try:

AC current from the shore power outlet goes down the black wire (I am using DC terms but bear with me) to the various appliances on the boat and then back up on the white (neutral wire). If you have any kind of fault- a short to ground in an appliance or wire then the current comes back on the green- the ground wire.

If you put an AC clamp on ammeter around all three wires you should see zero amps. The incoming black cancels out the outgoing white (or green).

But if you have a leak to the water (typically in the bilge) then some of the current will leave the boat through the water and there will be less current in the white or green wire and your clamp on ammeter will show some current.

It is a crude but effective test for AC leaks to the bilge.

But having said all of the above, AC leaks to the bilge don't cause what you are seeing. And I am not sure it is an electrolysis issue at all.

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Old 10-11-2014, 09:15 PM   #17
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And to drive home the point, less than 1 amp leakage into the fresh water can kill a nearby swimmer. Just do the test, take our word for it, and get help if your reading is not really close to 0 amps. And yeah, maybe nothing to do with the scale buildup.
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Old 10-11-2014, 10:44 PM   #18
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With your shore power disconnected, and your inverters, and generators output isolated, use an ohm meter between your AC neutral and ground.

You should see an infinite reading.

If you do not you need to find and resolve the issue.
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Old 10-12-2014, 12:04 AM   #19
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Quote:
Originally Posted by psneeld View Post
No I don't think so...IF you had a ELCI...it would trip if you had leakage..the reason they exist.

If you DON'T have one...and you get a reading on your power cord...you have an issue that needs correction.
>>> good and simple test to perform, thanks for the reminder

You won't get a reading if you have a fault that is leaking back out the green wire...so that one thing this test doesn't get I think....the test is more for leakage into the water.
>>> this fault (actually either fault) should trip shore power GFCI on the shore side if installed ... which leads me to the questions below ...
If there is a working GFCI on the shore side of shore power connection, is it really safe to assume that there is no AC current leak into the water and/or ground on a connected boat?

What is the impact of boat's galvanic isolator on shore GFCI's ability to detect the faults?
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Old 10-12-2014, 12:41 AM   #20
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An ammeter will tell you how many amps/milliamps are being drawn through the power cord. Any equipment that is on and functioning will add to the total. The meter will only read zero when there is no electron flow.
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