bob wrote:
Marine water heaters typically have two heating devices in one package.

The first is a standard 110V electrical heating element, connected
thru a thermostat mounted on the tank, more or less just like your
standard domestic water heater.

The second heating device is a coil of tubing inside the tank thru
which you can circulate your engine coolant.

Hi Bob,
Actually I was curious about the 12 volt heating device someone had
mentioned they had in theirs - would that one come with, or have
provision for inserting a thermostat or temperature sensor? Thanks