Water Heater Overtemp - Broken or ??

[Troubadour52993]

My water heater works fine on the electric element when I'm plugged into shore power, but if I'm out and need to run the engine for anything more than in/out of port, the overtemp relief opens. I basically need to turn off the pressure water pump, wait for the heater to cool down, then everything is ok again.

Is there supposed to be a thermostat in the cooling water">engine cooling water heat exchanger part of the water heater, that might be broken? If not, does anyone know of how I could fix? I'm thinking of putting a valve in the engine coolant line to the heat exchanger that I can shut if I motor for more than 30 minutes.

[svHyLyte]

IF the yacht has not been altered by a previous owner, perhaps when/if the original water heater was replaced, there will already be an OEM valve in the engine fresh water coolant loop to the heater that will allow you to dial back the amount of cooling water flowing through your heater. Your task, should you choose to accept it, is to find and adjust the valve but that can be a task given how tight some installations were/are. If none is found, adding a valve and by-pass loop isn' difficult, just a pain in the neck (again, given how tight some installations are),

FWIW...

[S/V Antares]

Remember that the shore side has a thermostat control that limits the heat to about 140F Your engine runs about 180F or higher. Is your engine running hot? What engine is it? I have seen inline reducers as well as ball valves. Has anyone seen an inline limiting t-stat?

[Troubadour52993]

The engine (perkins 4-236) runs about 185 according to the gage. I looked up Raritan and the overtemp valve isn't supposed to pop until 210 or 75 psi. After some contortion, I found the valve tag that confirms it is a 210 degree valve, so I suppose it is defective. I guess the task is to see if it is permanently attached/corroded to the heater if I can dismantle the setee.