Hot water heater.

[Peter Siemens]

I am curious as to how the water heater works when the engine is running. We used to heat up the water while connected to shore power but have since found that the water heats up when the engine is running. Is there an automatic power on feature switching it from 115V to 12V? It's a great feature but I would like to know how the switchover works.

 

[Ward]

It is not 12v it is the engine

don't know which boat you have, but most midsize and larger boats have water heaters that have an engine heat exchanger in them. This means that the water flowing through the engine to cool it is run through a heat exchanger in the water heater to heat water while the engine is running. This should use no power from your batteries

 

[Steve Dion]

Like a radiator.

Peter:as Ward pointed out the water flows from your hot side of the engine through the heat exchanger and the water heater. As the water flows through the exchanger in the heater it gives off the heat from the engine and heats the water in the tank.This is the same principal that cools the engine in your automobile with a radiator.