Bus Heater, Keel Cooling

I would like to put a "bus" heater in my Allweather. This boat is unusual in that it has keel cooling and dry exhaust. The boat is 30 years old and I am surprised that no one has ever put a bus heater in it. I have only had the boat a few months and am doing a major rehab. It is not in the water and hasn't been for 6 years or so. Any way I want to add a heater that runs off the engine coolant system. The existing system is very simple. From the engine mounted pump to the keel cooler then to the manifold and back to the pump. Do I just extend the system to the heater. Pump - heater - keel cooler - manifold - pump? I think there should be a bypass in case the heater core springs a leak. Is it this simple?

Post what your engine is. Pretty much any engine has taps where you can attach supply and return hoses for the heater. You do not want to put it in the loop going to the keel cooler. Best way is for one tap to be near the circulating pump suction, the other to be just upstream of the thermostat. That way you get flow through the heater even at light load where thermostat is closed or just cracked open.

Nice feature. I have one on my boat and having good solid heat without needing ac power is awesome.

Engine is a Yanmar 3HM.

I think that engine came from the factory with direct sea water cooling, no antifreeze. So if you have keel cooling someone adapted it. If so, it will have only one water pump, probably the original rubber impeller type. This changes things as there is probably only one flow loop. Then just put the heater in the flow path from engine to keel cooler.

Post some pics of the engine showing pumps and hose routing.

I got rid of all but one bus heater as they are so noisy. If you have the room, radiators work very well and are silent. I also built a manifold with a bank of valves so that each radiator is on its own loop; more plumbing but that way you can control heat distribution and even shut down rooms for sleeping etc. Daisy-chaining the bus heaters will not allow that control.

I run my entire system off of a Hurricane heater now as my cooling system (also keel cooled) was becoming too complicated so I tossed the heater heat exchanger and all its plumbing for simplicity.

Yes you are right. The engine was a raw water cooled model and was adapted by the boatbuilder for keel cooling. It uses the original raw water pump for the keel cooling circuit. It is close to 0 degrees F in the boat now and I don't feel like crawling around out there just now taking photos.

Understood. Zero F is not fun for boat stuff.

You can still do the bus heater, might not be quite as good of heat though. Also that is not a big engine and it does not put a great deal of heat into its water jackets.

I run a 450 Cummins and when running at low speed like 800rpm/6.5kts, the bus heater will suck all the heat out of the engine and coolant temp drops and heat gets weak.

Xsbank said:

I got rid of all but one bus heater as they are so noisy.

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"Red Dot" bus heaters, like the one in my buddy's boat, are quite noisy. Heatercraft Acu-Heat, which are the same sort of thing, are nearly silent, and very effective. I've had them in two boats for spring/summer cruising in SE Alaska, and they're excellent. In my 26-footer, it works so well I never turn it up past the lowest setting.

My heatercraft squirrel cage heater on low and medium is no more noisy than any of my other heaters and way more quiet than the reverse cycle units. Really can't be heard above engine noise which is quiet enough to hold normal conversation volume.

Down to 30 degrees outside the 40,000 btu heater warms the cabin to t shirt weather on my 40 footer which is a big saloon for a 40 footer.

My setup uses a heat exchanger so isn't as efficient as straight plumbed.

Great system going from port to port but once you turn off the engine the heat output declines very rapidly (Ive been told). Not the ideal set up except for when you are underway.

My 3HM35F (34.5hp) was freshwater cooled.

My present bus heater is very noisy and it almost never gets used. I just run the Wabasto. Can't hear it underway. And it makes more heat .. But my bus heater is not large. I have an old E-Spar unit that I've never run. Took it out of my Albin and bought a Wabasto. Never tried the E-Spar. I probably could be talked into sending it to you free plus freight .. Northland?

I made my own bus heater. Used an auto heater core, biggest one I could find, and an engine room squirrel cage blower. It is loud on high, but I set up a dropping resistor so it has a low speed setting. Most of the time low speed is sufficient, can't hear it over the engine/stereo/etc.

Ski,
Sure hope it's not the kind of electric motor that has problems w low voltage. When I get time I'll probably redo mine.

To me your idea of having a set of valves to shut off and bypass the heater would be ideal. I was contemplating putting this setup on my (current) water heater and (future) bus heater loops.

Trying to extend my season as well.

I use a marine (bus like) heater in each cabin/compartment. Also for forward window defroster. The baseboard radiators I replaced took almost 10x longer to heat a cold boat. Both of my mains can be tapped for heat when running. Also have a pellet stove and diesel stove with coils that can be cut in the loop. Some of my heaters have attachments for flexible hose to solve the cold spots. All are on thermostats that control valves. The heaters are 3 speed and I don't notice the noise, but I don't hear well.

Cappy, I made my own but look for hydronic heater manifolds at the plumber's shops or maybe Home Despot. Might save some effort. I also used Pex, which is easy to work with (plan your crimps ahead!) and cheap. Use lots of valves in case of bleeding issues and maintenance. Also, you will need a header tank. Hurricane makes a good one.

Xsbank said:

you will need a header tank.

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Mine is plumbed off the heat exchanger tank (which has the overflow tank ). Isn't that sufficient? The block mounted FWC circuit is plumbed from the outlet of the pump to the hot water heater, then back to the exchanger, then to the tranny cooling. I was thinking of just running the loop from the water heater to a bus heater then to the exchanger and tranny.


I am a firm believer in pex.