Replacing my water heater

[RodrigoDC]

You may be wondering why I post this on the engines forum. Well, I have a Yanmar 2gm20f engine, which has a hose coming out to my water heater, then another hose from the water heater back into the Yanmar engine.


I'm replacing my water heater for an electric one that does not include an engine hose intake or outake. Therefore, am I correct to assume that when I replace the water heater, I can simply close loop one of the hoses from the engine back into the engine (since I no longer have a water heater with this feature)?


Out of curiosity, what's the purpose of these hoses that feed to the water heater? Are these used to cool the engine using fresh water when available from the water heater?


I m attaching an image of a yanmar engine (not mine)that has the intake and outake loop that I believe I will need to to do replace the hose that now hoes into the water heater and back from the heater.




Any help would be greatly appreciated.

[Bowdrie]

Originally Posted by RodrigoDC

I'm replacing my water heater for an electric one that does not include an engine hose intake or outake.

Out of curiosity, what's the purpose of these hoses that feed to the water heater? Are these used to cool the engine using fresh water when available from the water heater?

Why would you want a water heater which will only work on electricity?
Being able to have hot water when running the engine is a great convenience.

Those hoses use hot engine water to heat the fresh water in the water heater thru an exchanger.
Nothing to do with any interface/flow between systems.
IIRC, a new engine will have pipe plugs in place of the hose barb fittings/
hose that's shown in the pic.
Being able to remove the plugs and add hose and fittings is a "feature", just like the heater in your car.

[RodrigoDC]

Originally Posted by Bowdrie

Why would you want a water heater which will only work on electricity?
Being able to have hot water when running the engine is a great convenience.

Those hoses use hot engine water to heat the fresh water in the water heater thru an exchanger.
Nothing to do with any interface/flow between systems.
IIRC, a new engine will have pipe plugs in place of the hose barb fittings/
hose that's shown in the pic.
Being able to remove the plugs and add hose and fittings is a "feature", just like the heater in your car.

Thank you for your reply, Bowdrie.



The reason I need to replace the old water heater is because the tank is leaking. Yes, I'd love to enjoy hot water while using the engine, but the difference between replacing the old heater with an electric one is about $900.



Are you saying that instead of using a loop hose, I can simply place plugs?



Thanks again.

[Bowdrie]

Originally Posted by RodrigoDC

Are you saying that instead of using a loop hose, I can simply place plugs?

Yes, that is the way a new engine would be delivered.

[Cheechako]

Are water heaters really that expensive now? Are you in Europe?

I find the engine heated units very useful personally.
Do you live aboard and only want it at the dock?

6 gallon with engine heat exchanger $432:
https://www.defender.com/product.jsp...311&id=2092171

[Lepke]

You can heat your electric water heater with the engine and a heat exchanger. Maybe find a used one on ebay. And you need a small circulation pump.
The loop you have goes to one side of the HE and the hot out goes to the hot water heater outlet. Put in a tee. And the heater drain goes back to the HE.

You can buy a small 12v circulation pump for less than $20 on ebay. There you can probably find a HE for less than $100 and sometimes less than $50.

[c.K.]

Originally Posted by Bowdrie

Why would you want a water heater which will only work on electricity?
Being able to have hot water when running the engine is a great convenience.

Those hoses use hot engine water to heat the fresh water in the water heater thru an exchanger.
Nothing to do with any interface/flow between systems.
IIRC, a new engine will have pipe plugs in place of the hose barb fittings/
hose that's shown in the pic.
Being able to remove the plugs and add hose and fittings is a "feature", just like the heater in your car.

Had to look into a new hotwater electric heater not to long ago around $600 can $$
Why not use the feature of having the engine heat up your hot water enroute?

[RodrigoDC]

Originally Posted by Lepke

You can heat your electric water heater with the engine and a heat exchanger. Maybe find a used one on ebay. And you need a small circulation pump.
The loop you have goes to one side of the HE and the hot out goes to the hot water heater outlet. Put in a tee. And the heater drain goes back to the HE.

You can buy a small 12v circulation pump for less than $20 on ebay. There you can probably find a HE for less than $100 and sometimes less than $50.

Lepke, this is a great idea, and will still allow for hot water with the engine without taking up much space.



The water heater I have is a Raritan, which costs about $1,000.



Yes, it is true that there are other, much less expend options. On Ebay, I saw a Kuuma 11811 Marine Water Heater 6 Gallon for $330 (https://www.ebay.com/itm/233125366089?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=Ln1w14_YTkS&sssrc=2349624&ssuid=wVZ2et3uTE K&var=&widget_ver=artemis&media=Copy). Unfortunately, it won't fit on my boat.



An electric WH, is more than I need, for the use I give it. I was only asking if I needed to loop one hose back to the engine or, as suggested, plug the in and out takes without causing any performance issues.


Thanks for the suggestions.

[RodrigoDC]

Originally Posted by Lepke

You can heat your electric water heater with the engine and a heat exchanger. Maybe find a used one on ebay. And you need a small circulation pump.
The loop you have goes to one side of the HE and the hot out goes to the hot water heater outlet. Put in a tee. And the heater drain goes back to the HE.

You can buy a small 12v circulation pump for less than $20 on ebay. There you can probably find a HE for less than $100 and sometimes less than $50.

Lepke, this is a great idea, and will still allow for hot water with the engine without taking up much space.

The water heater I have is a Raritan, which costs about $1,000.

Yes, it is true that there are other, much less expensive options. On Ebay, I saw a Kuuma 11811 Marine Water Heater 6 Gallon for $330 (https://www.ebay.com/itm/23312536608...mis&media=Copy). Unfortunately, it won't fit on my boat.

An electric WH, is more than I need, for the use I give it. I was only asking if I needed to loop one hose back to the engine or, as suggested, plug the in and out takes without causing any performance issues.

Thanks for the suggestions.

[Stu Jackson]

Originally Posted by RodrigoDC

Lepke, this is a great idea, and will still allow for hot water with the engine without taking up much space.

The water heater I have is a Raritan, which costs about $1,000.

Yes, it is true that there are other, much less expensive options. On Ebay, I saw a Kuuma 11811 Marine Water Heater 6 Gallon for $330 ..............
.......................
Unfortunately, it won't fit on my boat.

An electric WH, is more than I need, for the use I give it. I was only asking if I needed to loop one hose back to the engine or, as suggested, plug the in and out takes without causing any performance issues.

Thanks for the suggestions.

I don't understand Lepke's suggestion at all. The "heat exchanger" is right there in the water heater.

If you already have that Raritan, why not just hook up the engine's coolant to it? Are you actually saying your $1000 Raritan doesn't have engine coolant heating? I find that hard to believe. (I bought a Seaward 6 gallon for less than $300 in 2013.)

As far as plugging vs. jumpering the hose on the engine, I would suggest you be very very careful about plugging. While I have no experience with Yanmar engines, I do have a lot of experience with Universal freshwater cooled engines (25 years+). The engines come from the factory with that hose installed. When heaters are installed, they remove that jumpered hose and put the heater loop into it. In NO case have I ever heard of anyone plugging the hose connections. I strongly urge you to consult with Yanmar before you plug anything. It's probably easier to jumper a hose, anyway. Even easier to connect the danged new heater.

Good luck either way.

[Bowdrie]

Originally Posted by Stu Jackson

The engines come from the factory with that hose installed.

Amazing, I just looked at a brand new Yanmar on a display stand at an engine shop last week, no jumper hose.
Of course, Yanmar makes at least a Bazillion models.

[JoeRobertJr]

Originally Posted by Stu Jackson

As far as plugging vs. jumpering the hose on the engine, I would suggest you be very very careful about plugging.

I was just going to say the same thing. On my Universal, the engine coolant flow is:
engine coolant tank -> hot water heater -> engine heat exchanger -> engine block -> coolant pump -> back to tank
The hot water heater is not in a separate loop, so plugging would disable the engine cooling system.

[Simi 60]

We use hot water every day
But we don't run the engine every day
And on a sailing boat we would run it less again
So waste of money and effort for us to go engine heat hot water.

25 litre Rheem hot water system for us - cost $300
Comes on once , sometimes twice a day for 15 minutes at a time
Powered by solar , battery and inverter

[Bowdrie]

Look at the expanded pic that the OP posted.
it's a YANMAR engine, look at the BIG hoses, they are the main circulating system, the engine block/head is between them.
Trace the little hose(s) connections.
You can easily see that the loop for a water heater is a BYPASS system.
It just "taps off" some of the flow to circulate thru a water heater.
It's IDENTICAL to the system on your Ford or Chevy, and when you turn off the heater in your car the engine doesn't overheat because you have NOT stopped the flow thru the engine, you've just stopped the bypass flow.
The only difference is in the marine engine the radiator is replaced by a heat exchanger.
Edit, if you look at the hose at the right side in the pic you will see that it comes into the thermostat housing UNDERNEATH the thermostat, next to the temp sensor.
that "chamber" is common to the engine block/head, where the main circulating coolant is, and in no way blocks coolant flow thru the engine.

[RodrigoDC]

Originally Posted by Stu Jackson

If you already have that Raritan, why not just hook up the engine's coolant to it? Are you actually saying your $1000 Raritan doesn't have engine coolant heating? I find that hard to believe. (I bought a Seaward 6 gallon for less than $300 in 2013.)

Stu, the reason I cannot simply use the Raritan HE, as stated above, is because the WH is leaking. At the very least, I will need to pull it off the boat and inspect it thoroughly to find out if the leak is at the tank level, meaning probably dead, or at the outlet level, which I may be able to fix.


I wish I could tell you that these projects will take me a day and that's it. Instead, this usually means that the boat will be without a WH for a while. So, why not replace it with a cheap electric WH even if it's only while I figure out whats wrong with the Raritan?


So I was not asking whether I should replace the WH, I was just asking what I need to do to the engine regarding both hoses. I can plug them, or I can simply use one of the hoses as a jumper hose, I believe is what I've been told.


If I can fix the Raritan and plug it back into the boat, great. Then I can use the electric water heater in my house, and the boat will enjoy hot water when using the engine. Happy ending!