Engine coolant to hot water heater

Art Beaulieu

Art Beaulieu

New Member
Nov 21, 2020
7
Port Canaveral, FL
Boat Info
44 2007 Sedan Bridge, with 11.5' M350 Amanzi RIB with Mercury 40 hp
Engines
Cummins
I'm looking to run engine coolant from my 2007 Cummins QSC8.3 to my Kuuma fresh hot water heater. The questions is where to connect the draw and return hoses on the engine. Can anyone offer any advice, photos, or diagrams on how to do this?

My last boat with Yanmar engines had this and it worked great.
 
Tomco, Thanks for that link. Mechanics it seems are leery doing this without some guidance.

Have you had any problems with the install?
 
Make sure you have an anti-scald valve or thermostatic mixing valve on the hot water outlet before you do this. I disabled the hot water heater outlet on my QSC because the water becomes dangerously hot. That coolant comes out of the motor at around 170°.
 
I had this system on a Tiara and removed it. The water heater leaked and the engine coolant ran out of the engine into the bilge. Since your QSC uses coolant instead of raw water from the ocean I think it is a risk for the engine if there is a failure as I experienced. Your generator needs to be used with a load anyway.
 
Thanks Blue Yonder and becnme for the insights. I was planning on some sort of thermostat on the coolant side with a return bypass valve if that is possible. So one the HW tank is at 140º it shut off. Not sure if possible or practical.
The QSC uses both sea water and coolant.
 
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