Need Help...Shore Power Problem

[Surprise390]

I am really hoping that someone out there has some idea of what is going on here.
Here is what happened.
1) Everything fine tied up behind the house on Fri. 50a split into 2 30s.
2) Arrived at club Fri. Hooked up shore power 50a. Everything looked fine until I put a load on it, A/Cs, then I got a "reverse polarity" light on both circuits. Moved the cables 1 slip over, same shore power circuit of course, and everything worked fine for 2 days.
3) Arrived home Sun. Hooked up shore power and and applied a load which caused the port side volt meter to go from 110 to 0. Unplugged the 30s at the boat connects, reversed them, and now the problem is on the other 110 boat circuit. When I apply a load the volt meter goes from 110 to 0. Also, when there is no load the volt meter jumps around.
I have separate sets of cables for home and for on the boat and the problem occurs on both sets.
Everything runs perfectly off of the generator.
Any ideas would be appreciated.

 

[fwebster]

I think you have a bad connection where the shore power inlets connect to the wiring in the boat. There have been a few Sea Rays where the wires were not stripped far enough and the lug on the plug was screwed down on the insulation and wire. The result is enough connection to "see" 120V, but when a load is applied resistance increases and the connection fails.

Get this checked now, either by you if you understand electrical circuitry or by a marine electrician if you don't. Letting it go, even over night, could easily result in a burned wiring and a burned area on the side of the boat or a boat fire.

 

[Bel_Mar_Pointe]

I think you have a bad connection where the shore power inlets connect to the wiring in the boat. There have been a few Sea Rays where the wires were not stripped far enough and the lug on the plug was screwed down on the insulation and wire. The result is enough connection to "see" 120V, but when a load is applied resistance increases and the connection fails.

Get this checked now, either by you if you understand electrical circuitry or by a marine electrician if you don't. Letting it go, even over night, could easily result in a burned wiring and a burned area on the side of the boat or a boat fire.

+1 for a high resistance connection.

 

[Surprise390]

Thanks for your reply fwebster.
One more question though. Are the two 110 circuits on my boat completely separate? If they are, how would the problem migrate from one circuit to the other if I had a bad connection at one of the shore power connectors? They have worked fine for 5 years and even worked for 2 days after this problem first appeared. The problem is not the cables or the shore power so it has to be on the boat somewhere. Also, if the generator powers everything correctly then the problem has to be between the connectors and the panel. Help.

 

[fwebster]

The 2-30A circuits are separate as is the generator feed to the main panel.

This problem occurred on my boat.........when it was 6 years old. The insulation trapped in the lug eventually burns away. When it does, there is a smaller diameter mass of "stuff" in the lug, so it gets looser and resistance goes up as the insulation burns away.

In my case, the high resistance from he bad side caused the ends of the shore power cable to burn which caused high resistance on the other side when the cables were switched and that cause trapped insulation to burn on that side as well. Before I figured out what the root cause was, both shore power entrances were burned and the problem existed on both sides.

You have all the indicators of the same problem and I see nothing in your descriptions to rule out the cause I mentioned. Maybe I'm wrong, but this is something you need to have checked because it has the potential to burn your boat up.

 

[Surprise390]

Thanks. I'm going to start there.
One other thing. On my last boat, a 1995 370, I had a shore power connector toast a cable. Replaced the cable and didn't even consider the connector until now.

 

[Surprise390]

Wow...for the first time ever the problem was the first thing I checked and only took 2 min. to fix. One side of the home dock splitter was baked.