Marinco shore power adapter failure

[belizesailor]

Originally Posted by tanglewood

So in the interest of applying the tar and feathers where deserved, I think the “marinco” 30A 120V twist lock is actually a NEMA standard plug for that rating. So a US national standard, not a Marinco creation.

I think the fundamental problem is that it’s too big a plug/cord to hang from the prongs. All the problems follow. It’s just a matter of time.

Ironically, the marine 50A 120/240V plug is NOT a NEMA standard, but rather a Hubble proprietary design, and one apparently adopted by California for some application. But boats and marinas picked up on it. In this case it’s a large metal shell that takes the physical load, and is
much more suited to the plug and cable size and weight.

So if tar and feathers are to be applied, apply them to
NEMA, not Marinco.

And no, I have no affiliation with Marinco.

Given Marinco's dominance in the market I think their brand name has become akin to Xero...as in "make a xerox copy"...agree tar and feathers should be applied to those who continue to propogate the standard.

Given the number of fires/near fires caused by these plugs, Im surprised that insurers/marina's havent pushed back.

Of course, Marinco could/should get out ahead of the issue by offering a better solution, but too often those at the wheel of a near monopoly have long been asleep...just see BlockBuster, Kodack, etc...

[skipgundlach]

An observation on those overheat incidents:

I had a shore power connection go south on me as well, but it was the lousy connection on the boat-side legs which caused the heat, not the female receptacle.

With the locking ring secured, the faces should stay flush to each other, and the locking feature of the pins further assure it doesn't fall off (both assume you've rotated the plug and snugged the ring).

Of course, my failure is of a lug on the male house-power-style 15A end. That broken lug doesn't engage the new female end of my extension cord to the Honda 2000 reliably.

However, I have a workaround (that I don't like nearly as much, but it works) to put that shortened-end 15A male into the Honda output rather than my 12Ga extension cord, and mount my shore power cord (much heavier and more nuisance to avoid on the way back to the stern, where the Honda sits when charging) to it.

Power to the people so to speak, and I'm looking for a replacement, as annoying as that may be. But my original experience led me to removing the second shore power receptacle aboard and verifying my connections. It's the one I use, now, as we changed the configuration of the boat in our initial refit.

But the condition of the plug and receptacle which failed was noteworthy...

[Mistress Sirena]

Originally Posted by belizesailor

Marinco Plugs have very small surface area contact and the spring half of the connector is prone to distorting. Those factors plus a little corrossion can create high resistance at the contact points inside the connector. This can result in excessive high temps at lower than rated amps...a breaker wont protect against this.

Just a terrible design I have replaced far to many and can not imagine how many fires have been caused by these plugs even brand new will heat up long before 30 amps and just one time heated destroys tension on blade ie resistance short.

[Chotu]

Yet not a single person here practices good seamanship and properly connects their shore power cord using dielectric grease??

You wonder why you have corrosion which causes connectors to fry but you do nothing about it?

That's like not using zincs on your boat and wondering why your poorly made propeller and seacocks keep rotting out and sinking your boat.

Do the rest of us a favor so you don't burn down the whole marina. Start practicing a little good seamanship and protect your shorepower connectors with dielectric grease so they don't become a fire hazard.

Thank you.

[CharlieJ]

@Chotu
Dielectric grease may help but I have a problem putting an insulating material (that’s what a dielectric is) on an electrical contact. To each his own.

Corrosion may have caused this failure but I would bet my side cutters that the problem was the inadequate contact area between the male and female contacts and/or the loss of spring tension in the female contacts. High resistance equals heat in an electrical connection.

Just for the drama, here is a connection that I replaced about two weeks ago:

[skipgundlach]

Has anyone used something like this?

It seems like it might be easier to avoid getting the end wet as it would be easier to cover/shield in the event of rain:

https://smile.amazon.com/ABN-15A-30A.../dp/B01L2BLRAW

[Chotu]

Originally Posted by CharlieJ

@Chotu
Dielectric grease may help but I have a problem putting an insulating material (that’s what a dielectric is) on an electrical contact. To each his own.

Corrosion may have caused this failure but I would bet my side cutters that the problem was the inadequate contact area between the male and female contacts and/or the loss of spring tension in the female contacts. High resistance equals heat in an electrical connection.

Just for the drama, here is a connection that I replaced about two weeks ago:

If that's what your shore power cables are ending up like, you have nothing to lose. Humor me. Try it out. Try a little vasoline if nothing else. I'd be curious to see what happens. But try the dielectric grease ideally.

In a few months let's see if the cable ends up like the one pictured or not.

Really glob it on there and make sure everything is covered in it.

[zboss]

We have Smartplug on our monohull and our new boat has marinco twist lock connectors. After a few years experience with both I don't think we have arrived at the optimal solution. What we need is size and build quality of the smartplug blades and something with a much larger and more positive connection than the smartplug plug levers.

The levers are ultimately connected to a plastic plug using a pin. Those pins can pull out of the side of the plastic plug if the end is stressed - like someone accidentally stepping on it. The area where the pin seats in the plastic head can also elongate and become misshapen over time. So IMO, smartplug needs to get more robust in that regard.

I prefer the screw on metal ring connecting to a threaded connector over the smartplug levers but I prefer the smartplug prongs.

[rslifkin]

Originally Posted by zboss

We have Smartplug on our monohull and our new boat has marinco twist lock connectors. After a few years experience with both I don't think we have arrived at the optimal solution. What we need is size and build quality of the smartplug blades and something with a much larger and more positive connection than the smartplug plug levers.

The levers are ultimately connected to a plastic plug using a pin. Those pins can pull out of the side of the plastic plug if the end is stressed - like someone accidentally stepping on it. The area where the pin seats in the plastic head can also elongate and become misshapen over time. So IMO, smartplug needs to get more robust in that regard.

I prefer the screw on metal ring connecting to a threaded connector over the smartplug levers but I prefer the smartplug prongs.

You could switch to 50A twist lock connectors for the boat. They're a lot more robust than their 30A counterparts.

[BlackHeron]

Skip,

Just go get a new heavy-duty 15A male extension cord connector and put it on the adapter. There are nice plugs out there that are rated for #10 wire.

If you are plugging this adapter directly into any vertically-oriented receptacle the weight of the cord plus the 30A connectors and the 30A cord is going to continually damage the 15A male end. With the one-piece adapter you posted later in this thread it is going to be even worse -way too much weight sticking way out like a lever on that poor little 15A plug. I had one of those from Camco and it didn't last but a few weeks in a boatyard. It's also doing damage to the receptacle on your generator or the one at a yard it is being plugged into with all that weight.

My advice is to repair the male 15A end and plug the 30A side of the adapter directly into your shorepower inlet without even using your 30A shorepower cord. Then go out and buy a heavy-duty extension cord with regular 15A ends but with #12 AWG wire. I'm not sure how far your generator sits from you shorepower inlet but a 20' cord should probably do the trick. Whatever length you need, do it with the 15A cord.

Or, you could cut the female end off of your new 15A cord and directly splice it on to your old adapter to make your own custom generator-connection cord. This would still work at a boatyard when you are on the hard.

If I remember right you have a 2000w Honda generator. It is incapable of producing the type of juice to cause problems with a properly-maintained 15A extension cord unless you are running a hundred feet or more with a #14 or #16 gauge extension cord. There is no need to spend ridiculous money on a so-called "smart" cord chasing marketing hype. Take it from a professional commercial electrician. There are lots of couch-electricians here who never spent a day on the jobsite or in a classroom serving their couch-apprenticeships.

[BlackHeron]

Part duex,

This is exactly what I would do in your situation Skip.

Spend a whole $22.29 on this #12 cord from Harbor Freight. Cut it to the length you need and splice it directly onto your broken adapter so it reaches to plug in directly to your shorepower inlet with a little slack to spare. Now you have a custom generator hookup cord.

Splice it using regular yellow barrel splices and cover with a good marine shrink tube with mastic glue inside so the shrink tube overlaps the outer cord jackets on both sides by at least 2" or so. You don't need to go nuts staggering the splices or anything. It is REALLY hard getting them all even that way and then rhe individual wires will not sit right inside the splice.

Between the barrel splices and the cable jackets build that narrow area up with electrical tape so it is all even along the length of the splice. This just helps the shrink tube make a nice even covering and a more attractive splice that is better able to distribute the strain if it is being bent ir flexed a little. If you happen to have any nice rubber splicing tape designed for building up inside taped joints all the better but regular cheap vinyl tape will work fine here.

The shrink tube covering everything will do fine for strain relief if you overlay it a couple of inches on both sides and build up the skinny spots where just the three wires arell, so that the diameter matches the three barrel splices and the cable jacket. It may taper a little between the jacket and the barrel splices as three yellows may be slightly larger diameter than the cable jacket.

You can save that fancy 3-in-1 female lighted end and put a male plug on the other end of it later for use in the yard, or give it away on the cruisers net to someone who wants it.