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Old 08-04-2011, 05:57   #1
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Will my boat catch fire?

At the end of past season, I noticed these burn marks on my electrical cord. I know they were not there for the past 6 years. The difference with this past years is that I was using a Honda EU2000 portable generator. The burn marks are only at the boat connection. The other end is fine. I've included a picture of the adapter I use for the generator and 120v 20 amp shore power connection. It does not have any burn marks.

What's causing this?
What to fix it?
How to prevent it?

I would rather not just replace parts if there is some underlying electrical problem that needs to be addressed. Feedback would be most appreciated.
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Old 08-04-2011, 06:03   #2
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Re: Will my boat catch fire?

You have some resistance in the burnt pole of the connector (probably corrosion) which creates heat when the current flows through it thus causing the burning. The other connections are OK (low resistance) thus no heat build up. Replace both burnt male and female connectors and it will be OK.
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Old 08-04-2011, 06:11   #3
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Re: Will my boat catch fire?

If both of the shore power cords were burnt it may be a loose connection to the burnt pin on the boat. Heat was created by high resistance at that location. You should replace all burnt conectors, and make sure that all connections are tight. Also, use a polarity tester to verify proper power, neutral, and ground configuration.

There is no danger of catching fire if it is properly configured.
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Old 08-04-2011, 06:14   #4
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Re: Will my boat catch fire?

You need to periodically clean, and spray with a non-conducting, non-flammable lubricant. Especially if you ever drop them in the water. If not replaced, yes the boat will burn.
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Old 08-04-2011, 06:26   #5
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Re: Will my boat catch fire?

In the salt water atmospheric environment such burn marks are very common and as Wotname said, an electrical resistance has developed between the plug terminal and the receptacle terminal - the metal parts.
- - If you open up the receptacle housing/cover you will most likely find the same burn evidence and even burnt/fried wire where it connects into the receptacle.
- - If the external and internal terminals and wires are just blackened and not physically "melted/vaporized" away then just clean them.
- - Go to an electrical supplier (cheaper) or marine store like West Marina (expensive) and get a tube of dielectric silicon grease/compound. Clean and coat the wire strands that go into the receptacle/plug and coat them with the dielectric silicon. Do this also to all the wires (not the insulation). Then likewise, maybe using an artist brush, coat the blade/receiving terminals with the dielectric compound. then reassemble the units.
- - Every so often and especially when "plugging in" to a new dock box coat your ground power cord's blades with more dielectric silicon. I even use the brush to force some into the dock box receptacle, but normally just liberally coating your plug is enough.
- - The dielectric silicon's only job is to keep the salt water air from coming in contact with the metal of the wire and plugs/receptacles. It acts like a barrier but does not affect the actual transfer of electricity.
- - As you work on the boat's electrical system it is a good idea to coat all the accessible terminals and terminal block metal screws/pads with the same dielectric silicon compound. This will go a long way to eliminating the blackening and resistance build-up in your boat's internal wiring system and help prevent resistance fires from occurring.
- - The downside of using dielectric silicon compound is that everything is "greasy" and it gets on your fingers. But again that is a very minor thing compared to going a long way towards preventing electrical fires. Or in the case of shore power cords, having to purchase a new one. They are not cheap.
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Old 08-04-2011, 06:31   #6
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Re: Will my boat catch fire?

At least you knew to ask about the issue before you set fire to the docks.

Twice or three times locally (Lake Ontario/Erie) in the last ten years, multiple boats have been lost when electrical faults set fire to boats...an almost always avoidable fate.
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Old 08-04-2011, 06:40   #7
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Re: Will my boat catch fire?

I second osirisail's use of Dow Corning 4 silicon grease (DC 4).
FWIW, we had all sorts of minor corrosion problems in instrument connectors behind the instrument panel of a Grumman Mallard flying boat until we started using DC 4 on every connector; after that the problems were very few and far between.
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Old 08-04-2011, 06:51   #8
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Re: Will my boat catch fire?

I believe a big part to this problem is you need strain relief or your cord. The moving of the boat works the plug and causes this condition
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Old 08-04-2011, 07:21   #9
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Re: Will my boat catch fire?

These burnt cords are a result of arcing and not just resistance on the plug or outlet. In many cases it is because the plug is not securely locked in the outlet. It can be movement from the power cord as the boat moves around in the slip or as a result of a failure of the outlet, the connections at the outlet are not making positive contact with the plug. In any case, you probably should not use the power cord as is and the outlet should be replaced. You have the option of just replacing the plug on the cord or buying a new cord. Chuck
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Old 08-04-2011, 07:31   #10
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Re: Will my boat catch fire?

Hmm... the male contact on the bulkhead connector doesn't show any evidence of arcing - well not that I can see from the photo so I suspect it is more likely to be a loose connection in the female contact of the lead or corrosion in the same connector.

Regardless, you need to replace them.
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Old 08-04-2011, 07:35   #11
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Re: Will my boat catch fire?

All of the above!
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Old 08-04-2011, 07:47   #12
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Re: Will my boat catch fire?

There is a hardened copper slot in the female connector that the male slides in to. Over time the vibration and just use will relax the "bite" that these female plugs have. The male on the boat may still be 100% functional. Wise, it would be, is to remove it and check the screws that anchor the wiring to the male plug. Heating and cooling cycles tend to loosen the screws. Almost every time it's just the female that gets loose, creates heat and transfers the heat to the male causing the black spot you see on the male part.

I have had real good luck at electrical supply houses and Hubbell marine fittings, plugs and cables. You will generally find that they will be 50% less than a boat yard or nautical supplier even though they are the same product. You don't have to pay the "boat tax".

I wouldn't use that plug any more until you get a new female cord end and check the wiring on the male end.
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Old 08-04-2011, 13:01   #13
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Re: Will my boat catch fire?

First of all...consider yourself very, very fortunate!!

The NMEA plugs that we all have used for years were never intended for marine service. If you dissect one you will find that there are dimples in the female receiving slots that are designed to engage, through spring action, the holes that you can see in the male plug. There are two problems with this arrangement; first, the twist part of the twist lock has to occur so the dimples line up with the holes. But over time this spring engagement gets weaker and weaker until you have a poor electrical connection.

The Hubbell hardware is definitely robust, but as one that has made up literally dozens of these, there are just too many parts. It took me three tries this week to finally get a 50A/250V male Hubbell made up to my satisfaction!

I strongly recommend replacing the shore power inlet and the boat end of the shore power cord with the system developed by SmartPlug. It meets the ABYC E-11 standard and it appears to be strong enough that you could tow the vessel with it! It also has a thermo switch internal to the plug that will open the circuit when the plug temperature > 200F.

They cost about $50 more than a stainless setup from Marinco or Hubbell. The 30A system has been out for some time and 50A/250V will be out in the early Fall.

Here is the site: SmartPlug Systems - Shore Power Products and Accessories

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Old 08-04-2011, 16:49   #14
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Re: Will my boat catch fire?

Thanks so much! It looks like I have a path for upgrade or repair.

Do you think the burnt female shore power cable connector can be replaced? I THINK the cord I have is a solid molded piece (i.e., not servicable). I beleive I would have to cut it off to attach a new one. Would a replacement have the same integrity?
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Old 08-04-2011, 17:30   #15
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Re: Will my boat catch fire?

you need to check your grounds in the boat's electrical system--solitary bird had that problem-- i had ground defects for a bit before i bought boat.
she wont burn yet-- just fix her. this one was done by a 3k honda--i burned the generator-- it had problems also, but no mas--lol--
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