Shore Power Cord Economics

13 Dec

Unfortunately, as in the photo above, the connectors on shore power cords often get toasty. It always seems to happen on the neutral connector (white wire in the US system) and I don’t know why. Maybe the electrons get all gummed up and dirty from being on your filthy boat, then get stuck on the way off?

Sometimes it happens on the male side too, and the guts of the shore power inlet have to be replaced:

At any rate, a burned/melted shore power cord is bad, and should be repaired, but therein lies the rub. The new connector for the end runs about $35, but that’s not all. In order to make it like before you also need a new boot, which you can buy with or without the threaded ring, but call it another $15:

So now we’re up to $50 (prices vary, but you get the idea) in parts alone to repair a shore power cord. Fifty foot, 30 Amp shore power cords sell for as little as $80, if you shop around. It’s fairly straightforward to re-terminate a shore power cord, which a do-it-yourselfer can easily do. It takes me about ten minutes, but it’s easy to see that the cost of parts, plus the cost of a marine electrician quickly makes the cost about a wash.

To do it right you’ll want some good wire strippers, a cable stripper (judicious use of a box cutter will suffice), a cutter big enough to lop off the whole fried end cleanly, then it’s nice to have a multimeter or AC tester to check that you haven’t reversed something that will really make things burn. So the task becomes daunting without all the proper tools, and if you don’t have the right tools they’re not cheap.

So what are we to do? It’s terrible that we live in such a throw-away society. I once toured the second largest open pit copper mine in the world, in southern Peru, and it’s no small feat to get copper out of the ground and turn it into copper wire:
Peru 059

So alas, if you just need to replace one end of a 50-foot, 30 Amp cord, repair costs enough less than replacement that you should fight the good fight and do it, if you can do it yourself or your electrician happens to be around working on other things anyway. If you have to replace both ends it’s cheaper to just buy a new one. If the whole cord is looking fairly tired and sun-baked, then definitely replace the whole thing.

If it’s shorter than 50 feet, it’s probably not worth repairing it.

For 50-Amp cords the whole magilla gets much more expensive for either repair or replacement, but the economics are about the same.

Copper wire should always be recycled, but finding where to do this can be a pain. As a marine electrician I take a big box to be recycled every year. Back during the height of the economic crisis people were desperate and copper prices were at an all time high, so shore power theft was common.

This article was syndicated from The Adventures of the Vessel Condesa


  1. Ward Ferguson

    Mark, Not true as the neutral only carries the inbalance between the two hot legs therefore. it cannot exceed the amperage of one leg i.e. 30 or 50 amp.

  2. Clark Beek

    Bob, I’ve seen those things around and always assumed they were a European version…or something. Looks robust, and definitely an improvement, but not cheap. Looks like it’s got the regular 30A connector on the dock box side and the improved connector on the other end of the cord and on the boat inlet. Most of the mischief seems to happen on the boat end of things, so the SmartPlug probably solves the issue. Good tip!

  3. Bob Atkins

    The standard L5-30P plug and socket are just way too flimsy for regular connect and disconnecting. They were never intended for such service. When the shore power connector on my boat and the cord started showing signs of thermal stress instead of using another crappy L5-30P plug I decided to convert to a SmartPlug.

    The SmartPlug is way more rugged and engineered for repeated connecting and disconnecting. In addition the boat side receptacle has a thermal breaker in case something causes the connection to heat up.

    The conversion was ridiculously simple. The boat side perfectly replaced the original L5-30P receptacle. Four screws, disconnect old recaptacle, connect the new one to the boat wires and put it back in with the same 4 screws. Took maybe 15 minutes. It was almost too easy.

    Next, I cut off the old L5-30P from the shore power cord and attached the new plug – it was a bit trickier to do but the kit included a handy white plastic cone and along with a little dielectric grease I was able to properly feed the power cord through the block rubber strain relief. My only complaint is that the female cord end housing isn’t as robust a a material as I would have liked to see. I added a tie wrap on the cable just inside the shell to provide more robust strain relief to the cord to keep the cord from being pulled out of the plug.

    Now almost 4 years later after many connect/disconnects there isn’t even a hint of heat stress or oxidation. Mechanically the plug shows no signs of wear. I am very happy with this and I highly recommend these to replace those flimsy and outdated L5-30P plug and sockets!

  4. Guy Colson

    Actually. in a typical 3 wire 230v. cable, there is 230v. between the two “hot” wires, and 115v. between each “hot” wire and the neutral. But each “hot” wire is 180 degrees out of phase with the other, so the current running through the neutral wire is always LESS than either of the hot wires. In face, if the current on each “hot” wire is the same, then theoretically there is no current at all running through the neutral – they cancel each other out.

  5. Mark Capalongan

    By way of a preventative measure, I’ve had pretty good success with DeoxIT D5 as a periodic cleaner and conductor rejuvenator. Spray the contacts once a week or so.

    I suspect that on many circuits there are actually two hots with 220V between them and one neutral with 120V from neutral to each hot. That allows for two 110V circuits but the downside is that there is twice as much current on the neutral so that’s the one that overheats.

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