Water heater for yacht with direct cooled engine

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Fairwaystraveller

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I have just removed a "condemned" Vaillant gas water heater from my Southerly 100 and was wondering if anyone had any recommendations on the best way to get running hot water on a yacht with a direct sea-water cooled engine (i.e. cannot use the engine cooling water to heat a tank.) The kettle suffices for now, but it would be good to be able to have a nice warm shower!
 
The easiest way would be to replace the heater with a Hydronic Eberspacher (other makes are available) and a calorifier.
I have one, 5 Kw, with a 20 litre calorifier and that's enough hot water for most uses. The hot water also goes through a matrix to provide blown-air heating to the aft cabin.
I don't have the engine plumbed into the system.
 
See this page http://coxengineering.sharepoint.com/Pages/Calorifier.aspx of my website. Some raw water cooled engines, e.g. Bukh, Yanmar, maybe others, have plugs that can be removed to fit suitable nozzles for the hose supply and return. Other engines may not have such plugs but it is perfectly possible to arrange an alternative, by drilling and tapping or by substituting hoses with branches.
 
You certainly can get hot water from a raw water cooled engine. My Volvo Penta 2003 28Hp engine is connected to a calorifier and I get lovely hot water without any problem to sink and heads tap. Volvo do the connection parts and I am sure others will as well.I realise you probably not have a Volvo as you have a Southerly.
 
Our Yanmar 2GM20 ran the hot water through a calorifier before being injected into the exhaust elbow .. so it can be done.
 
fireball said:
Our Yanmar 2GM20 ran the hot water through a calorifier before being injected into the exhaust elbow .. so it can be done.
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That method is not normally successful because water being ejected from the engine to the manifold is a mixture of heated and bypass (cold) water that normally has a temperature of about 40C, nowhere near enough to heat a calorifier. I believe that the Yanmar thermostat arrangement is identical to that of the Bukh. If Yanmar have come up with a clever idea of their own I would be delighted to know how it is done, please.
 
vyv_cox said:
That method is not normally successful because water being ejected from the engine to the manifold is a mixture of heated and bypass (cold) water that normally has a temperature of about 40C, nowhere near enough to heat a calorifier. I believe that the Yanmar thermostat arrangement is identical to that of the Bukh. If Yanmar have come up with a clever idea of their own I would be delighted to know how it is done, please.
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Erm - can't answer the question because it was on a boat we owned over 6 years ago. IIRC whatever we had worked quite well - but as it was installed prior to us buying the boat I hadn't fully investigated it.
All I do know is that we did have a calorifier (that also had a 500w immersion heater) and it produced nice hot (subjective - always hot enough for me but SWMBO likes it scalding!) water.
 
Slight drift here, my boat has a Perkins m30, it has a wheelhouse which gets chilly in the winter. Its been on my mind for a while to fit a car heater matrix in the WH just on the deck near to where my feet go to warm the place up a bit, the run for the pipes to the matrix should be no more than 10" feet, could it be done easily?
 
Thanks all for the info and the leads which I will follow up. The engine is a Yanmar 2GM20. I think that the thermostat used for raw water cooling is set at a much lower temperature than for indirect / fresh water cooling due to sea water crystallisation at higher temperatures. I've read that this makes the water temperature too low for heating via a calorifier but if there's information out there that says differently I will give it a go! I already have an Eberspacher hot air system on the boat which (after a re-build - another story!) is very effective. As a yachtsman I am of course looking for a relatively low cost option! Thanks again for comments and ideas!
 
Your info is incorrect, as you can see on my website. There are hundreds of Bukh 20s running calorifiers. As my site says, when I had one the tap water was too hot to touch after 30 minutes of motoring. Raw water cooled thermostats are typically low 60s opening, plenty hot enough.
 
Fairwaystraveller said:
Thanks all for the info and the leads which I will follow up. The engine is a Yanmar 2GM20. I think that the thermostat used for raw water cooling is set at a much lower temperature than for indirect / fresh water cooling due to sea water crystallisation at higher temperatures. I've read that this makes the water temperature too low for heating via a calorifier but if there's information out there that says differently I will give it a go! I already have an Eberspacher hot air system on the boat which (after a re-build - another story!) is very effective. As a yachtsman I am of course looking for a relatively low cost option! Thanks again for comments and ideas!
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Having a pair of raw water cooled 3GM30s I have looked into this in some detail. The temperature of the water coming out of the block is plenty hot enough to heat a calorifier. The problem is, as has been said, that the water coming out of the block is mixed with the cold bypass water in the thermostat housing. The thermostat valve not only opens the flow from the block but cuts off the bypass flow. It would be possible to modify the thermostat housing to keep the two flows separate but it's beyond my metal working skills.

At full cruising revs, the thermostat is fully open so all the water going into the exhaust has gone through the block and could be used in the calorifier. Unfortunately as soon as you revert to tickover, some cold comes from the bypass and that would cool the tank. One possible solution is to have a manual changeover valve so you only put water through the calorifier when the engine is under load.
 
I have a perkins 4108 and heated a calorifier by tapping freshwater coolant from the air bleed holes in the head near the #4 injector and the exhaust jacket (it has a dry exhaust for several feet before sea water is injected) BUT it lost all the heat again fairly rapidly. I thought it was being sucked back into the engine and unsuccessfully added a non-return valve in the heating pipes , but having just read Viv's page referenced above, could all the heat be flowing back to the freshwater tank??? I disconnected it in disgust as we still have a gas geyser, but would reinstate it if it could be made to work properly.
 
All sounds very complicated. I had to remove the geyser or the gas engineer wouldn't replace the cooker and flexibles and the insurance surveyor probably correctly said that the location of the Vaillant in the heads was a CO hazard (although it had been original Southerly equipment.) Has anyone experience of the Whale 12v water heater (http://www.whalepumps.com/Marine/pr...2V-Water-Heater-11-ltr-3-US-Gal-Electric-Only) ? wonder if the alternator is man enough to power it on a yacht?
 
chrishelen said:
Slight drift here, my boat has a Perkins m30, it has a wheelhouse which gets chilly in the winter. Its been on my mind for a while to fit a car heater matrix in the WH just on the deck near to where my feet go to warm the place up a bit, the run for the pipes to the matrix should be no more than 10" feet, could it be done easily?
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I have a deck saloon ketch, with a Volvo MD22 59hp. I got a heater matrix from a Transit van at the scrappies for a tenner, A 3" duct fan (IIRC £teens). It works a treat. After all, every car has a heater, why not a boat?
 
Fairwaystraveller said:
I have just removed a "condemned" Vaillant gas water heater from my Southerly 100 and was wondering if anyone had any recommendations on the best way to get running hot water on a yacht with a direct sea-water cooled engine (i.e. cannot use the engine cooling water to heat a tank.) The kettle suffices for now, but it would be good to be able to have a nice warm shower!
Click to expand...

I had just such a set up on my previous boat. Raw water cooled Volvo 2003 and calorifier. I struggled with it for several years and it never really worked anything like as well as the Vaillant on the previous boat. I spoke to Volvo, something you could do in those days without being fobbed off to talk to a dealer and they confirmed that the system didnt really work even though they had supplied it direct to Moody. Sure it will get water a bit warmer after an hour or so running but thats it.

In your position I would definitely replace the Vaillant..
 
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