The Offshore Voyaging Reference Site

Q&A: Which Heating System?

Question: What do you use for heating on Morgan’s Cloud?

Answer: We have an Espar D8 8KW (I’m not sure of the BTUs). It is one of the bigger ones they make and keeps us toasty in all weathers. One thing I would suggest is not to use the exhaust exit in the hull that they normally specify. In heavy weather this will be very vulnerable to flooding. We had Mike Bowden at Ocean Options, where we bought the heater, fabricate us a 4′ high chimney with a ‘Charlie Nobel’ type top that is braced to the stern rail. With this set up we can use the heater even in very heavy weather, which is, after all, when you want to be toasty below.

If I were doing it again I would install one of the Espar heaters that uses hot water and radiators or heat exchangers. It would be more controllable and it would cut down on all the ducting though it would be more complex to install.

We also have a heater that uses the waste heat from the engine to warm the cabin—essentially free heating with no fuel cost.

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David Higgs

I’m in the process of buying a Hylas 54 – based in the UK . She’s really well equipped, apart from one detail. The heating is is from the Cruisair Air Conditioning. This either needs shore power or the generator running to power it. If using the generator, only two of the 3 units can be powered as the generator is 24v DC and provides 240 AC through an inverter. I want to use the yacht year round and, as the reverse cycle decreases in efficiency as a heat source as the water gets colder it doesn’t seem ideal. As I obviously have blown air ducting putting in a hydronic 24v boiler in system would seem to be the solution. Does anybody have experience of this problem? I’ve had Eberspacher before, but loath to put another blown air system in.

Marc Dacey

Hi, David. We have a similar Marine Air 12,000 BTU heat/cooling unit, which becomes less effective in colder water. We have a smaller boat (41 feet), but heating merely the saloon with a diesel heater and using 12 VDC fans to send warmth to the pilothouse (which gets a lot of solar heat) and back to the aft cabin seems to make more sense than duplicating the heating system a second time. It depends, of course, on where you intend to cruise and when and whether you require shore independence.

Another idea is using some sort of radiant heat from the engine routed to those parts of the boat you want heated, but that introduces plumbing problems and complexity I would find personally dodgy.

David Higgs

Hi John & Marc,
My instinct is with you John – if you take a heat exchanger off the engine you have another way of getting heat in, along with an Eberspacher . Like the idea of diesel heater, but John has outlined the issues there. Domtec do a Hydronic Diesel Boiler which works with air con, but that really is only viable if you can run the whole system on 24v – don’t want to be running through the inverter off batteries. I’ll investigate this further. Tempting to take the air con out – but I can imagine my other wonderful half questioning my wisdom, if we end up sweltering somewhere under the sun. Agree about heading up North – that does solve all issues to do with air con if you don’t have it.

Marc Dacey

David, there are worse problems to have with a Hylas 54! I think it really depends on where you want to take the boat and how you wish to use it. Offshore, even if I had the capacity, air con would seem an extravagance if I could rig airscoops and 12 V cabin fans. On a dock, in winter “layover” mode, perhaps in England, you can lay money that I would run the Marine Air unit until the water temp. disallowed it, AND I might run a diesel heater so I could have one area “warm” and the rest of the boat (aft cabin and forepeak workshop, for instance) merely “cool”.

That said, I would prefer for sub-8C conditions something like the Refleks due to the simplicity. Yes, it’s not instantaneous, but yes, we are on a boat, where chilliness is predictable. With diesel stoves, a lot of damp goes up the flue…a positive to me. I concur with John that “simple can be hard” and that you really have to line up your logical ducks to fully justify effort and expense. Sometimes the answer is “put on a second sweater, dear”…perhaps not an unpopular choice, but a realistic one.

Clearly, where John and Phyllis sail is about 15 degrees N of sweater waters!

Bill O'Brien

Does anyone have experience with the Webasto hydronic heaters? I’m planning on putting a central heating system in my boat (Tayana 37) which would supply me with domestic hot water as well as heat. Anything I should be aware or concerned about re: hydronic vs forced air. I’m assuming forced air would reduce the possibility of condensation but I would need a separate water heater and the duct work would take up much more space and be harder to route. Either system is expensive so if I’m barking up the wrong tree……

Bill O'Brien

Thanks John,
I won’t be installing my heating unit until the spring of 2018 so have a bit of time to do some research. Thanks for the heads up on the Webasto reliability issue. I only want to do this once so I’d like to get it right. Definitely leaning towards hydronic!


Hi Bill:
I had a Webasto hydronic heating system installed in my sailboat 6 years ago to heat the boat and the hot water. It has worked flawlessly, not done a thing to it. First thing in the morning I fire it up for about 45 minutes. It warms up the boat if needed and I have hot water all day.

Bill O'Brien

Thanks for the update Stan. Don’t suppose you’re located in Nova Scotia?


British Columbia.