Cabin heat from diesel engines

[bix85]

I'm considering a refit of an older catamaran that has a Yanmar 3gm30 (raw-water cooling - no secondary closed cooling system) in each hull. The engines need to be overhauled, so adding an additional water pump to each could be done (I think easily?) This would allow a heat exchanger to be added.
The boat originally had a propane heater, but that was removed because it quit working and the boat was in the tropics.

My question is: in trying to extend the cruising range to Maine in June should I try to convert the engines and add engine heat? Should I just add a propane or diesel heater? Should I add both?

Thanks,
Ron

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[Sailmonkey]

Just add a propane/diesel heater.

Unless you like running your propulsion engine for just heat. And unless you're actively motoring, not just at high idle, there isn't that much heat to be had.


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[a64pilot]

What he said, but I'd stay away from propane as it is heavier than air

[UNCIVILIZED]

Propane fueled heaters, from what I understand, add a lot of extra moisture into the cabin, as a by product of their combustion. Which you don't, of course, want, when it's cold outside. As such will just magnify the condensation problems which you likely already have, when the thermometer starts dropping.
Where as, diesel heaters, produce a dry heat. And so, aid in managing the moisture issue.

Regardless of which you choose, it's probably worth doing the numbers on installing water heating coils in, or next to/around, your heater(s). So that you can more efficiently spread the heat around your boat. Particularly given that it's a catamaran, which has several different "zones" which will need heating.
That, & look into installing 2+ heaters. One in each hull perhaps, plus possibly one for the bridgedeck cabin.

You can get Refleks heaters with such coils, built in. And there's a little info & feedback on a few different types of heaters, here on Beth & Evans's site Top Rated Equipment

Refleks's website is definitely worth visiting, too. Especially when you consider where the units are made. Plus, their target audience.
I mean guys who live & sail that far North (Professionally), in waters which never really warm up, must know a thing or three about heating boats.

Also, making sure that your boat's well insulated is Huge. To the point where it'd make sense to borrow a Thermal Imager of the sort that's used to check for heat leaks in homes (gratis I think, or for a small fee at most).

When I insullated my 1st boat, the results were giant, & immediate. And it took me all of a weekend to do, with; closed cell foam, 3M Spray Glue, & automotive headliner carpet + trim.

[Sailmonkey]

Un-vented propane adds moisture, by something like a vented propane bulkhead heater won't add any moisture. The combustion gasses all exit up the flue.


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[bix85]

Thanks for the info. I'll focus on diesel, since I have plenty on board, and because propane is heavier than air.

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[Dsanduril]

Originally Posted by Sailmonkey

Un-vented propane adds moisture, by something like a vented propane bulkhead heater won't add any moisture. The combustion gasses all exit up the flue.

+1. On average diesel is ~14% hydrogen by weight, propane and butane (and hence LPG) are ~17-18% hydrogen by weight. Both produce moisture as a product of combustion, so it is all about the heater design. An unvented heater will introduce the moisture into the living space, a vented one won't. In addition to the moisture you also get the CO, CO2, and other combustion products, so you really don't want an unvented heater.

You'll find more unvented units in propane since propane doesn't tend to soot or stink, whereas an unvented diesel heater would be objectionable to the nose and paint. Regardless, an unvented heater (even the catalytic ones) is an invitation to problems in an enclosed space, and particularly the small enclosed spaces of a typical boat.

[raqsshaqi]

have you looked at Mikuni website,just fit the 2 kw unit and you have hot water then fit a coil in/on the hot water tank and use small car[mini] heater matrix with 12/24 volt fans,you are then too hot so can always shut the system and use a thermostat to control circulation pump,it is not difficult.
S Y Raqs Shaqi
Larnaca
Cyprus

[Dauntlessny]

Originally Posted by bix85

Thanks for the info. I'll focus on diesel, since I have plenty on board, and because propane is heavier than air.

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Yes, Good idea.I did Maine and Nova Scotia in July and AUgust without any heater.
It was OK.

[UNCIVILIZED]

I should think that the ducted, forced air heaters would be good options for catamarans. Given that you can route, & or re-direct the heat to whatever part of the boat that you desire. And should also be able to regulate how much of it gets routed to where, I'd imagine. As those types of systems are a lot like what you find in homes.
Their drawbacks being; unit cost, & the space taken up by the hoses/ducting. But they're very popular in the PNW.

And while I'm not at all knocking the propane systems. Especially as, from what I know of them, they're easier to both install, & use. But it seems to me, that the vast majority of the professional/commercial boats use diesel based systems
Thus, that'd be where I'd start my search.

[Liam Wald]

Originally Posted by a64pilot

What he said, but I'd stay away from propane as it is heavier than air

I have a Dickinson bulkhead mounted propane fireplace/heater.
This device is very efficient, and in my estimation very safe.
I have been using this fireplace for over ten years.
I pressure test the system every couple of months or so and never an issue.
I don't worry about it any more than I worry about the Force Ten propane stove/oven.
My guess is that neither the fireplace or the stove will ever be a problem...
and if they are I will only know about it for a nano-second or so!

[Dymaxion]

Webasto or Espar diesel units work well. 12\24volt versions, hydronic or hot air heat. Hot air is easy to duct around. And lighter! Have thermostats , just set and forget. Or manual/timer controls. They have a very small exhaust duct to contend with, so cabin stays clean/dry. Search for "AirTop"

[Liam Wald]

Originally Posted by a64pilot

What he said, but I'd stay away from propane as it is heavier than air

a64Pilot,
What fuel do you use to cook with aboard your boat?

[Liam Wald]

Originally Posted by Dymaxion

Webasto or Espar diesel units work well. 12\24volt versions, hydronic or hot air heat. Hot air is easy to duct around. And lighter! Have thermostats , just set and forget. Or manual/timer controls. They have a very small exhaust duct to contend with, so cabin stays clean/dry. Search for "AirTop"

I have heard that these are quite good and heat the boat quickly.
How many amps do they require?

[Dymaxion]

AirTop unit requires 1.5-2.5 amps at 12volts. Lots of Webasto bits to build a nice ducted installation on FleaBay, not sure about the Russian cloned versions I saw there.