Source of hot water while cruising

[abotha]

For a catamaran:
Water 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.

[Hunky Dory]

Have a look at the Coleman propane camping hot water portable heater, it heats the water and also has a shower option.

[CaptTom]

Originally Posted by Hunky Dory

Have a look at the Coleman propane camping hot water portable heater, it heats the water and also has a shower option.

I never knew such a thing existed. I can see it being very useful on a boat.

I was looking at this one on Amazon.

[wingssail]

Originally Posted by CaptTom

I never knew such a thing existed. I can see it being very useful on a boat.

And there are products like this which make your galley and shower work at anchor or sailing.

Runs on propane, but there are quite a few people who fear propane.

Around $150

[john61ct]

https://youtu.be/ghj5V5cUo1s

[SVRocinante]

Originally Posted by sguerrero1971

I just installed a 12volt 200watt hot water heater element with a thermostat to use with my Solar. I don't have enough usage out of it to be able to tell you if it will work long term, but it was easy to install and I'm hoping between it using the motor our generator and the solar we can have hot water when ever we need it.

Submersible DC Water Heater Elements - Missouri Wind and Solar

I've seen a lot of mention of Propane, just thought I would throw this into the mix too.

Thanks squerrero1971!
I just finished installing solar on Rocinante and now, along with my wind generator, have excess electrical power! How would’ve thunk it? ��

Anyway, I’m now looking at these 12v heating elements to replace/augment the 110V element in my Isotherm water heater.

[Marathon1150]

Once the right latitude is achieved, ambient temperature water, in the cockpit with a bit of a breeze, is preferred

[SVRocinante]

Originally Posted by Marathon1150

Once the right latitude is achieved, ambient temperature water, in the cockpit with a bit of a breeze, is preferred

Ah, yes! The ultimate solution!

[kristjan]

Just a QUICK B3 hot water tank, engine waste heat, but idle is low however turn it on through the inverter and the alternator is charging also. But usually just boil a kettle of water, so I can have a coffee also, and have a quick cold shower. Hot water for sure for wife and kids to shower, Or I feed the Honda 2000 to the shore power inlet. Can make brownies in toaster oven at same time then, a half hour of that and there’s hot water, fresh brownies and a hot coffee. I use a Victron multiplus inverter, rarely motor to move boat, I’d rather plug the Honda and put it at the bow when sailing for an hour to charge up.