HOT WATER Dumb question of the day.

A

Alexander

New member
In our diesel inboard powered boats we had the ability to route heated water from the fresh water cooling system through the heat exchanger in the water heater so we had nice hot water at the end of each cruising day.
I have never owned a big outboard engine powered craft and I was wondering if anyone has figured out how to make an outboard produce the same hot water.
 
There have been reports of folks who ran hoses from outboards--but none I am aware of in C Dory land. Most of us rely on "sun showers" in the smaller boats without water heaters. With the water heaters the Honda 2000 is the favorite--although some are using the Yamaha 2000 or 2400.
The other option (which I am not crazy about) is some thing like the Zodi or Coleman propane fired almost instant water heater.

The ones which use the outboard heat, tap into just off the thermostat. There are issues with the water not being hot enough to work in the relatively inefficient heat exchangers in the water heaters. The other issue is another set of hoses to run up under the gunnel and to the water heater. A round trip run of about 30 feet.

We have had excellent results in our Tom Cat and 25 with the Honda EU2000. We had air conditioning, the water heater, and a high output battery charger for the battery dedicated to the freezer/refer combo. So there were other uses for the generator.
 
I've not done it and can't imagine a way to do it. Outboards are using fresh cool water right out of the pond that may not get to a usable temperature for heat exchanging to a water heater. I suspect it would be quite a plumbing hack job to make such an idea work, but who knows.

I remember an old Evinrude sign that showed a guy with a lathered face, in the water shaving using the bypass water from the running engine. Evinrude was touting that as a feature. I have often wondered if the guy didn't get mighty sick breathing the monoxide coming off that engine that was exhausting right in his face. Not to mention that the prop was about crotch high and within a few inches of his unmentionables.
 
Thanks for the info. Looks like the little gen set is the simple and reliable way to go. I just have a lot to learn about the ins and outs of these little beauties.
 
Thanks Flyer , that's pretty close to what I was thinking was possible. Every engine makes heat, it's just determining if it's feasible to harness it.
 
The problem with both of these "hot water" is that it is not really hot and not at a high volume. The first one wanted warm water to stick inside of his wet suit and either warm it before diving and/or after coming out of the water. The second one was warm water (it turned out to be about 120 degrees). Neither of these would do to heat the water in a normal marine water heater, which basically uses a cylinder in the center of the tank to heat the water in the tank. There is not going to be enough temperature differential, by the time run thru all of the tubing to get to the water heater.

The diesel will have water running very close to 180 degrees, and in good volumes, after it has gone thru the engine block, and then to the water heater before going thru the heat exchanger. We also hooked up a diesel to supply about 25,000 BTU thru a "Red Dot" heater, when the cooling water (closed system--vs open system for outboard), was returning to the heat exchanger, and then back to the coolant tank.
 
Thanks all, I'll be going with the little Honda generator (When I get a CD) which will do much more than just heat some shower water. It can be my household back up during hurricane season too, if I haven't taken the boat nort for the summer. Bob
 
Dr Bob, may I ask what type of hot water you used with your Honda 2000i. I have the same gen, just added a house battery charger, AC going in this winter, hot water is next, haven't even researched it yet. Thanks Roy
 
The instant-demand water heater shows a 3600W power consumption.

What would the 1800W Honda 2000eu do with this? It may overload and shut down. At the very least, the heating would not be sufficient at only 50% of the requirement.
 
The Chronomite water heater that Marc linked to is 3600 watts, and there is also an 1800 watt version (probably what Marc was referring to). Even the 1800 watt version is going to be too much for the Honda. The Standard water heater on the C Dory is 1500 watts and will run on the 2000 Honda. I am aware of some folks putting the 240 volt water heater in these, and that will only draw about 750 watts, and can be run on the 1000.

I tried one of the flow thru "instant" water heaters, but it turned out that at least the one I tried is not made for continuos pressure, but rather is to be used when the faucet is open and no real pressure on the tank. I had hoped to recoop the space the 6 gallon tank occupies. There may be some instant tanks which will withstand the pressure, and that would be a good option.
 
Thanks Marc & Dr Bob, started my research, so far looks like the Chronomite SR 15L is close to what I'm looking for. Only want it to take WARM showers with it when on the hook, no need for constant HOT water. Though at 1800 W & 15A it will max out the Honda 2000i, but I was planning on turning all other 110V appliances off when showering, so it should work. Heck it might "clean the carbon out" of the genny!! Still using the solar shower, but always looking to upgrade, Roy
 
I would be leery of the Honda running at 1800 watts output for any more than a few minutes. Some of the ham radio operators have mapped output vs time. They are able to get 2000 watts for a few minutes, 1800 to 1900 watts for up to 30 minutes (before the unit shuts down--my guess is that there is a thermal shut down circuit in the inverter section). 1600 watts all day long--on full power. Eco power does not work well with the higher loads.

If I was going to run 1800 watts full time, I would go with the Yamaha 2400 watt unit. The unit is rated at 2000W / 16.7A continuous--2400W / 20 amp peak. The unit does weigh 75#--a lot more than the Honda. The Yamaha is also more difficult to use a long run tank with.

I did find a 2.5 gallon flow thru heater which only uses 1500 watts:
Ariston 2.5-Gallon Electric Point-of-Use Water Heater at Lowes. That might be more practical...
 
Dr. Bob, Thanks again for all the info. I was only going to run my Honda 2000 for the 4 minute 2 gallon quick shower, so the 1800W usage should work. But the Artiston GL 2.5 also looks good, 1500W, and it holds 2.75 gallons of hot water. These 2units are a lot better than the ones I found a few months ago when I started thinking about adding hot water. Roy
 
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