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Old 07-19-2012, 02:34 AM   #1
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Default Heat Exchanger for water heater, Raw water cooled engine.

First Post. On my 06 2700 SE I have a raw water cooled 350 mag. Hot water heater works fine when hooked up to shore power. I'd like to have hot water while at anchor, boat is in saltwater and often at Catalina with no shore power. I don't want to run a 2000W portable generator for a half hour to get a hot shower on day 2. Has anyone else plumbed the hot water heater to run off engine heated water? I realize there is a heat exchanger in the hot water tank, in addition to the electric heating element. I should be able to tap into the exhaust heated water and plumb it through the water heater heat exchanger and out a through hull fitting. So long as I freshwater flush after every trip I should be ok? Any input is appreciated. Thanks!
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Old 07-19-2012, 12:29 PM   #2
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Well,

You would need to replace the water heater from only electric, to the duel unit..... going to guess $400 for that at least.

Then you should be able to connect heater hoses off the engine water pump, like your car heater, you need the block hot water behind the thermostat, so your not burning $12 of gas to take a shower.

The manifold water line is suppose to be cool water to cool the manifolds.

Next problem is your only going to push clean water thur the heater with that little 12v fresh water pump, so its going to be a tinkle hot shower, and cold water.

So, cost vs. use?

They do sell this little solar shower thing in the boat store which is nothing more then a bag or water on a rope, that sits in the sun all day, and then has a hose on the bottom, or try the solar panels, to do the same.

Your limited more by the 12v water pump then the V8- hot water making machine.
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Old 07-19-2012, 01:02 PM   #3
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My hotwater heater uses both, though when I repowered I didn't reconnect the heat exchanger for the hot water heater. There should be two lines, one into the hotwater heater and one back out again. This is aside from the freshwater in/out. The outflow goes back into the exhaust and ported with the rests of the engine's raw water. There is no need to install a new through hull, besides that exhaust water is going to be HOT.

Check whether yours already has a heat exchanger. If there are an additional pair of In/Out aside from freshwater, then you should be able to hook it right up. Mine are black metal barbed connectors. Some are on the front, some are on the back, some are on the side. $400 would probably be the highest you would need to pay if you needed to replace it. If I recall it used to tap off of the raw water side of the heat exchanger. I can't remember if it went back into the heat exchanger since i removed it a few years ago.

BTW, how large is your hot water heater? My Honda 2K takes about 15 min. (20 tops) to heat a 6 gal. water heater. I'm not sure how much shorter it would take to idle your engine. I can tell you that I idled for about an hour a few weeks ago to try to recharge the house battery a little. The cockpit got very warm sitting on top of the idling engine. Just a thought.
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Old 07-20-2012, 05:07 PM   #4
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Thanks for the input. This is a dual unit, plumbed for use of engine heated water as well as the electrical element. Ive done the generator method, but its one step I would like to avoid. We dive and surf off the boat quite often so a hot transom shower is a welcomed luxury. Our water in So Cal doesn't ever get warmer than 68(NOT a complaint), so its nice to fill a wetsuit and rinse with warm water. Water pressure does not seem to be an issue. The factory installed transom shower and cabin shower have plenty of power. I will definitely look into plumbing the hot water back through the exhaust, but a very experienced mechanic suggested the through hull fitting. I did it on my last wellcraft and it worked well. Water coming out of that fitting was quite warm. Used a valve to control the flow, found that too much flow cause the temperature gauge to not get a solid reading.
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Old 07-20-2012, 09:29 PM   #5
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hey there, the tank does not get plumped to the exhaust. The inlet to the water heater is plumped from the top of the intake manifold right beside the thermostat housing. The exit line out of the water heater goes back to the engine and must be hooked up to the water pump. This is the only way you will get the water to circulate and have sufficient heat. After only a small cruise, I can be at anchor for hours and hours and the water is still scalding hot, even the next morning the water is very very warm, it only take a few mins of idling to heat it again. The maxum parts websight has all the drawing on how to hook it up.....good luck....cheers
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Old 07-21-2012, 02:24 AM   #6
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Could you be so kind as to post a link to the drawing?
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Old 07-21-2012, 04:07 AM   #7
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Hello there, just click on the boat you want to look at.

http://www.maxumcustomercare.com/catalogs_index.html
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