I did all my testing with a meter... I wanted to ensure that the connections were all good and there were no shorts before applying "30 amps of high voltage."

I tested through the shore power cord, through the shore power connector, thru the breaker panel, and then to each individual socket... dragging around the shore power cord in the boat as I went from outlet to outlet using that as one end of the cord as my test lead. (I was testing both for shorts and loss)

I only have 6 outlets, plus the water heater and the battery charger. But I did notice some odd readings like white connected to green... and that prompted me to check that particular outlet... which is how/why I found out all the metal electrical bits were essentially being held in place by the incoming wires and the corroded pins. Wiggle it just right, and instant short.

I will replace all the outlets, and if I can figure out what is down stream of what; I will use GFCI at a few, otherwise they will all become GFCI. GFCIs are fairly cheap "insurance." What I don't like about them is the lack of a good weatherproof cover if you are only using one outlet.

Now the real question... are Home Depot GFCI the same as West Marine GFCI... 'cause the ones at WM cost twice as much.