Intro & Hot Water Heater with Atomic 4 Question

[BenCT]

I just bought a 1980 C&C 36 with the original atomic 4 engine in Norwalk CT. I’m new to Atomic 4s. There is a hot water heater on the boat, a Seaward S700, that has an intake and output to attach to a heat exchanger in an engine for supplemental hot water heating. However, I have a raw water cooled late model Atomic 4 that doesn’t have a heat exchanger. It looks like the PO had the hot water heater just looping to itself and not using the heat exchanger input/output. Meaning there is a tube on the hot water heater that attaches the heaters input and output for the exchanger water together. Does this make sense? I don’t see where or how the hot water heater could be attached to my raw water cooled atomic 4.

[Al Schober]

To use your A4 to heat the domestic water, you'll have to convert the A4 to glycol cooling and install a 180F thermostat. Your glycol loop would then go from the engine, to the water heater, to the heat exchanger, then back to the engine. It can be done.
The real issue is: Do you want to?
How much hot water will you have? I'll guess maybe 5 or 6 gallons at 180F. You can probably stretch that to 10 or 12 gallons by using a mixing valve to bring the output down to 120F.
How many people taking showers? Are you willing to be the last person taking a shower? Hope you like it cold. Most of my guests had no concept of a Navy shower.
What worked for us (3 folks on a Tartan 30 for up to 3 months) was Sun Showers - those solar heated things. Heat them up during the day, shower late afternoon. Everyone had their own shower bag. When it ran out, you were done. Really made us appreciate getting into a marina that had showers, even if we had to put coins into a slot and play 'Beat the Clock'.

[ndutton]

Conflicting opinion

You can certainly heat your potable water with a raw water cooled A-4 although as Al implied, it won't work as well or efficiently as an anti-freeze cooled engine with its own heat exchanger - - - but it will work. Your water heater's internal exchanger connects inline in the hose that currently runs between the exhaust manifold and the vented loop. I suggest pressure testing the water heater exchanger before proceeding though. There may be a good reason it was disconnected.

However, converting your engine to anti-freeze cooling is the single best and most important upgrade you can do regardless of your water heating plans.

[BenCT]

Thanks to both responses. I think after this season I will look into the fresh water system for the obvious engine preservation reasons. I’m not looking for the extra hot water, I just wanted to make sure I wasn’t missing something and my logic was sound that the hot water heater wasn’t hooked up to the A4 and I was missing it. Thanks again.

[alcodiesel]

...and welcome to the forum.