No power on one leg.

cmills wrote:
The legs are separate. The third prong is neutral. Ground is a metal plate around the plug. Also, it's a reverse twistlock, the plug is female and receptacle is a male.

You are on the right track - replace the female plug on the other end (shore end)of the power cord with a male plug.

Since you are dealing with a modified electrical system carefully check the wiring from the new male plug all the way back to the rigs CB panel including the twist lock plugs and make sure it's wired correctly. You just never know what else might have been changed.