I very often come across sockets where the detent or dimple & hole really don't feel as if they have meshed up and locked into one another. I have learned over the years that this is due to the clamping mechanism in the female socket weakening over time and getting loose.


This weakening is likely exacerbated by movement in the cord and plug as the boat moves. It may also be due to the rather thin metal used in the clamping mechanism of the socket?


As you can see here the metal used to create the clamping force on the male pin is a mere 1mm thick in the NEMA L5-30 socket...