A couple years ago we installed new marine grade (Marinco) shore power inlet connectors, having moved them from the outside of the boat where they were subject to constant salt spray to being just inside the cockpit. They connected to the main electrical panel through 30 amp breakers. Recently my helper, who was staying on the boat during nights as he worked on it during the day without me there, woke up to this scary mess. If you look closely you can see the power is still on to that yellow cable... The shore power cable was only a few months old.
The wires in back of the unit were covered in soot but undamaged. So all the heat had clearly been generated in the connection itself, not in the wiring. The load on the failing circuit at the time was judged to be about 1500 watts (a single electric heater).
As you can see, the center of the connector, including all 3 of the connector tines, are simply gone! So this was less of a fire per se and more of an arcing situation. The only way for this metal to completely disappear is to have been vaporized via arcing.
We used 10 ga marine approved wire for the connection and if you measure from the connector to the panel and then back to the connector it is no more than 50 feet. 10 ga is the recommended gauge for 30 amps at that distance. But we know that the problem was in the connector, not in the wire.
Needless to say we bought 2 brand new connectors and then created a custom polished 316 stainless backing plate for enhanced fire protection going forward.
The final result (before refinishing the gel coat) is shown below. Better, stronger, faster: We can rebuild it...
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