It really doesn't matter what size the cord or boat wiring is if the weak point is a spring loaded recptacle. As an electrician in the oil field and residential/industrial sector, and as a maintenance lineman for the local electric coop, with years of upfront experience at POU services (point of use) we found that one of the worst offenders for burnt up service was spring loaded apperatus. Sometimes it was the meter base or the old style fuse holders, regardless, spring loaded contacts invariably lose there "spring" and get hot then burn up. The first thing we tried was adding extra spings to the existing lugs, this helped but was not a perminant solution. We even resorted to ct/pt based services on anything rated over 100 amps, that was to expensive. Then Cutler Hammer came out with a leverage lug based meter can. Problem solved. I think I can design a similar setup for 30 or 50 amp boat receptacles, any takers ?