For a catamaran
system is usually a low pressure system. Remove calorifier
hoses from motor
and attach to hydronic water heater
. Could be Eberspacher or Webasto. I prefer Eberspacher. i would do this one for each hull
Depending on how many guests, either run one or both water heaters to heat up the water tank. For my wife and I we will only start up the port side heater
. No need to start up the engine
For a 53ft Royal Cape Catamaran
i would use the Eberspacher Hydronic M12. Uses min 0.15 lt / hr diesel
. Max (on turbo startup mode), 1.2 lt / hr diesel
Speak under correction but last time I had a look at a Yanmar fuel consumption
per hour it was comparable. So no unneeded wear and tear on motors. And you already have diesel on board.
You could of course keep the motor
hoses running to the hot water tank and add the hydronic heater hoses. But I have not seen a low pressure hot water tank that has so many in / outlets. Unless you add the Eberspacher to the existing motor hoses and each time you run the water heater you heat up the motor as well. Not sure if this is good or bad.