Re: Melting Marinco plug on my Honda EB3000 generator.
Well, that means that the electricity run through the plug generated heat faster than the plug could radiate the heat away. That happens for one of two reasons. Either there was more current than the plug could handle or there was high resistance where the plug's contact meet the receptacle.
Overcurrent situations happen when the load (i.e. your electrical system) is running too much stuff or has a short or a similar kind of fault. If this is what happened, then you also have a problem with the generator -- the circuit breaker should have tripped.
High resistance situations almost always come from one of two things. The plug was not properly seated and therefore did not have good contact over a large surface area, or else one or both sides of the connection offered high resistance because of dirt or corrosion that prevented electricity from flowing across the entire contact area. When normal electrical flow is concentrated in a small area of the plug, it works just like overcurrent situations but on a smaller scale and generates heat as a point source.
All contacts, both male and female, should be clean, free of corrosion, and dry. It's a quick check. Just eyeball the prongs and the receptacle every time you use the generator. Cables should be good for years of service. If they are dirty and corroded, you need a drier, cleaner place to store them. What about the cover of the receptacle on your boat? Does it keep the female plug clean and dry?
T. P. Donnelly
S/V Tranquility Base
1984 Islander 30 Bahama