There is a mixer valve on the hot water heater itself (hot water output) which allows you to adjust the temperature via regulating how much hot water is coming out and getting mixed with cold water - this allows you to stretch your hot water tank longer and prevent scalding from the heat exchanger heated water. There is no adjustable thermostat on the webasto/indel/isotherm 11g hot water heater. If you are getting hot water while cruising, but not while plugged in with the water heater breaker powered on, my guess would be you have a problem with the element, and it needs to be replaced. I had to do this recently, due to an overheat sensor failure which caused some melted wires and the element to burn out, and so I had to redo the wiring harness and install a new element. That was up there on my list of "un fun" projects due to the difficulty in draining it/access... here's a quote from the website on the set temp (non adjustable):
Electrical Heating at the Dock —
Isotemp Spa Water Heaters are equipped with a nickel-plated copper electric heating element and an electrical thermostat set at 167°F (75°C) - hot enough to prevent bacterial growth. A thermal cut-out feature protects against overheating should the tank run dry.
