Marathon Water Heaters

[cmillsap]

Marathon installed two Atwood Marine EHM11-SM Water Heaters in my coach. They are stacked one on top of the other. They are made of stainless steel and should not get rusty and start leaking water for many years. However, the control relays, thermostats and heating elements that are attached to the water heater can and do fail and need to be replaced from time to time to keep the water heaters operating correctly.

Don’t bother calling Atwood for replacement parts as they have no idea how Marathon designed their systems. Marathon stocks the parts in their Coburg location.

Both water heaters are controlled by a thermostatically operated relay located on the upper water heater (see pic #1) (old style).

Marathon Part # 106607-01. Thermostat, 110-170DEG. Cost is $29.10.

That relay is an updated version of the original relay and requires a wiring modification when installing. If I understand correctly, the relay directs 120V power to the upper water heater element first. When the water temperature reaches the adjustable setting on the relay’s thermostat, it then switches and directs 120V current through the lower water heater thermostat (pic #2) to the lower water heater element.

Marathon Part # 107649-01. DISC, SNAP, W/RESET, 190DEG. Cost is $26.87.

When replacing either of these thermostats, be sure to apply a good amount of Heatsink Compound between the two surfaces of the thermostats and the water heater to ensure that the thermostat is able to read the water temp correctly.
Pic #3 shows the wiring modification required when replacing the old style to new.