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**a64pilot** · 13-12-2016, 09:02

He needs a heater that is less than 1 cu ft, and short rolling your own, I don't know of one. 1 cu ft will hold 7.5 gls, subtract the tank of course the heat exchanger and insulation and its going to be tough to get 5 gl.
Only water heaters I know of with a liquid to liquid heat exchanger are marine ones so I don't know if there is another source.
Perhaps an on demand one mounted outside of the boat on the railing? But as has been pointed out the on demand ones waste a good bit of water while you wait for the heat?

Cheechako · 13-12-2016, 09:03

If not going to use the AC option. I wonder if you take the inside tank and heat exchanger out of a 6 gallon if it will fit in your space? You would have to insulate it and devise a way of anchoring it.. But maybe getting rid of the sheet metal box will help?
The other option is mentioned, have a tank made up to fit a purchased heat exchanger replacement.
I once made a kerosene tank out of an old fire extinguisher. You know the nice chrome/SS ones from the 50's with the screw on bronze cap? They used to be all over salvage yards for $3. The bronze cap was easy to tap and drill etc. Mount your heat exchanger in the cap. :>)

HopCar · 13-12-2016, 09:22

Take a look at the Isotemp Spa series of water heaters. They have a four gallon with heat exchanger, stainless tank and mixing valve.
The mixing valve lets you set the temp higher than you normally would. It mixes in cold water as the hot comes out and lowers the temperature to a safe level. The effect is you get more usable hot water from a small tank.
Isotherm SPA Water Heaters

jkindredpdx · 13-12-2016, 09:27

Quote:

Originally Posted by boatpoker

Not that it's important to everyone but none of these propane units meet ABYC Standards.

True and if one were to install an https://www.eccotemp.com/eccotemp-l5...-water-heater/ anyway they would want to run a LPG line back to vented tank locker and also have a dedicated charlie noble.

HopCar · 13-12-2016, 09:32

Just checked the dimensions of the Spa 15 heater. It's 12" in diameter but it is 18" long. It would be a little too long for your space.
https://www.indelwebastomarine.com/u...aters/new-spa/

johnwasielewski · 13-12-2016, 10:33

I have a 6 gallon stainless heater from Johnson Pumps. Works off heat exchange and i couldn't be happier with it.

**a64pilot** · 13-12-2016, 11:30

Hey Hopcar
Tank ships tomorrow, do you have the pump, hoses fittings et all rounded up yet

RidgeRunner · 13-12-2016, 11:53

This one might fit, it's only an inch bigger than your specs:

Defender.com Search Results: 501182

I had this model on a previous boat. It only has a 3 gallon capacity. You'd think it would heat up much faster than larger units, but it actually took a lot longer to get up to temp than larger heaters I have used. I never hooked up the AC power, I only used it with the engine. I'm guessing it must have a fairly tiny heat exchanger.

Sailuke · 13-12-2016, 12:45

Quote:

Originally Posted by Shrew

What are the dimensions of the space you're trying to fit into??

I assume by not plugging into A/C also means you don't have a generator of any kind?

No, no Gen. Its only a 27 foot boat

Cheechako · 13-12-2016, 12:54

Would the 6 gal fit in the lazarrette if you made a shelf?

accomplice · 13-12-2016, 13:00

Just a thought.... at a certain point when reducing size you've gone from a coil and tank to simply a coil. So... why not use a simple heat-exchanger? It'll require that your engine be running and up to speed in order to get hot water, but if your tank is very small that will also be true.

You can get marine-grade heat exchangers that are quite small. If you wanted to get fancy by attaching automatic mixing/ temperature limiting/etc. you could. If you want to keep it simple, small and cheap you might just use it straight ... but be careful. You might also find swimming pool heat exchangers made of stainless steel and/or copper or brass.

fatherchronica · 13-12-2016, 13:16

We have found many folks very happy with the on demand propane water heaters. No heat loop though, as they don't store any water.

Scott Berg · 13-12-2016, 13:53

Isotemp for sure makes small ones but I agree, make one! Weld up a stainless box, insulate it; buy the heat exchanger from Torrid Marine or their OEM. If you aren't making an electric one it shouldn't be that hard and it could be any size you like...