Marine Water Heaters–Camping and Boat Showers
We talked about the luxury and decadence of hot water showers in our previous article, “Boating and Camping Showers.” This article goes a bit further, with specific application toward our configuration. While the specifics are, — well, rather specific, — the principles apply across most marine hot water systems. The essential elements are an engine with freshwater cooling capacities, a heat exchanger, and a hot water heater that can take advantage of the he heat exchanger.
Marine Hot Water Heater Replacement
3 years ago, we upgraded our precious 1962 26′ Pearson Ariel, the “Gwa’Wis, to a 1978 Endeavor 32′ sailboat, the Agadda Da Vida. On the Gwa’Wis, we had no pressurized water nor any hot water system. We poured water from a 5 gal. jug and heated water on the stove for most of our needs. For showers, we used our Zodi shower and a few curtains. Since acquiring the Agadda Da Vida, we have upgraded and repaired her. We have tried to anticipate our future wants and needs. When we purchased the boat, it had a few known deficiencies. Among others, was that the hot water heater was leaking. This was not really surprising as the water heater was nearly 35 years old. It only leaked while the engine was running so we were pretty sure that the deteriorated piping was in the engine cooling to water heater heat exchanger.
Marine Engine Selection
Our engine, a Yanmar 2 QM20, was cooled solely by sea-water circulation. No fresh water involved. One problem that this created was that, even if we left the dock with a wholly heated water tank, as soon as we started the engine we were effectively cooling off our hot water tank. Not the best thing.
When considering a replacement, we looked at a variety of factors. The first and most important was of course space. Second, was toward control and future expandability.
Hot Water Heat Exchanger
We finally selected an Isotherm Slimline Stainless Steel water heater. Our price was about $680.00 from James Town Distributors, (http://www.jamestowndistributors.com/userportal/product.do?part=54605&engine=adwords!6456&keyword=product_ad_1537&type=pla). The old water heater had to be cut apart in order to remove it from the installed location. It was apparently installed before the deck was laid down and there was no way to remove it intact. The Isotherm would fit through the hatch without taking it apart. The Isotherm offered stainless steel construction, multiple mounting options, 115 v operation, and a low enough amperage draw that I could run it from my 1500W power inverter if needed. It also allowed plumbing for engine water heating.
As initially installed, prior to an engine change, I installed shut-off valves for the engine water so that i wasn’t cooling off my hot water every time I started the engine. It was a bit inconvenient but worked. A year and a half later, I replaced my old engine with a new one that was fresh water cooled with a heat exchanger to the raw water. This was a Yanmar 3 YM30, with outlets for freshwater heat exchange.
With a bit of re-plumbing, mostly eliminating a lot of valves and “T’s, we now have seamless hot water supply wether at dock, underway, on generator, or at need, inverter. Our hottest water is while the engine is running. About an hour of normal cruising will bring the 6 gal tank to very hot water. An hour or so on dock or generator will do the same. My battery power is somewhat challenged in trying to heat a full tank, but can usually manage it. If the batteries start to run low, I can always fire up the engine or the generator though that has seldom been necessary.
Water to water heat exchanger
It is such a luxury to have readily available hot water for showers, dishes, face washing or whatever, that I will never regret the investment involved. It is miniscule compared to the benefit derived, especially if you are boating with people less acclimated to minimalist accommodations.
A pleasant and comfortable cruise, with a few accommodations, can make all the difference between a begrudging companion and an advocate boating partner for life.
Think about it!