I do not know but.......
Steve:Given that no one else has suggested anything, I would question the possibility of a calcium build-up on the electric heating element. Do you have hard water at the dock? I have had that sort of problem in my home unit, where the heat from the element is insulated from the water by the calcium build-up and the element overheats before the water gets hot enough to satisfy the thermostat. Although I have a 336 myself, I am not sure what your options are regarding testing or replacing the element.Wish I knew more. Sorry I cannot be more assistance.RodneyS/V Avanti