Emmanuel

Water heater replacement

10 posts in this topic

Hi, I'm replacing my water heater (6 Gal), mercruiser 350 with heat exchanger as it is totally corroded and leaks. When unmounting it I realized the red hose was totally clogged. Don't know since when, as I bought the boat last summer. 

I don't know whether the exchanger uses sea water or is a closed system with coolant ?

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You should have a heat exchanger, mounted on the engine if its a closed system. Now I am not talking about the water heater. There should be a radiator cap to check the AF. If thats not there, than you have an open system so sea water is running though your block. 

I have a closed system and my hot water tank rusted up too. I installed a Isotherm tanks since its made with stainless steel, uses less power and heats up faster. I did need to flush the engine since the rust from the hot water tank got into the engine.

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Thanks IGGY, that's really clear. So I have a system with sea water.

I'm now waiting for a new heater, to re-install everything. Only the heater was clogged, full of rust, as I have tried to start the engine just after having withdrawn it to see what would happen (the hoses coming from and toward the engine being free with nothing connected on it.) I saw the water was coming through , and decided to stop the engine immediately to avoid having too much water inside the boat !

I have read some people were connecting the 2 hoses together to have the water circulating inside of it. Is this the way you make sure no rust stays in the engine ?

Also when everything is fixed, I guess it means, when using the engine, I can have hot water without having to press the heater switch on, right ?

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I have heard some boaters bypassing the hot water tank like you said. By connecting the two hoses, BUT I would only do that if your 110% sure that you will never heat the water off the engine. But if your not connected to shore power, than yes. You can heat the water off the engine. It will take about 20 to 25 minutes. If your engine is cold, you need to warm up the engine and the engine needs to warm up the tank. This is another reason where a closed cooling system is better. Your hot water tank will heat up faster. You would have AF running though it, rather than sea water. 

Heating the hot water off the engine is great and we do it all the time when we go away. 

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I don't have a closed cooled system and my Hot Water Heater rusted out.  I did just connect the two red hoses bi-passing the Water Heater and it's been running just fine for a three months now.  What alot people don't know is that there is actually a zinc that needs to be changed out that is located at the end of your plumbing.  BoatUS Magazine released a detail article on how to find the zinc to repair it and included a bunch of pics.  Once you get your new heater, make sure you locate this zinc so you change it out periodically.  I just ordered my new heater as well. 

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30 minutes ago, Water Dawg 6 said:

I don't have a closed cooled system and my Hot Water Heater rusted out.  I did just connect the two red hoses bi-passing the Water Heater and it's been running just fine for a three months now.  What alot people don't know is that there is actually a zinc that needs to be changed out that is located at the end of your plumbing.  BoatUS Magazine released a detail article on how to find the zinc to repair it and included a bunch of pics.  Once you get your new heater, make sure you locate this zinc so you change it out periodically.  I just ordered my new heater as well. 

Was your water tank aluminum? W

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3 hours ago, Water Dawg 6 said:

I don't have a closed cooled system and my Hot Water Heater rusted out.  I did just connect the two red hoses bi-passing the Water Heater and it's been running just fine for a three months now.  What alot people don't know is that there is actually a zinc that needs to be changed out that is located at the end of your plumbing.  BoatUS Magazine released a detail article on how to find the zinc to repair it and included a bunch of pics.  Once you get your new heater, make sure you locate this zinc so you change it out periodically.  I just ordered my new heater as well. 

Yep! I have a closed system so I need to change the anodes in the heat exchanger. Rather than the hot water tank.

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Changing those zincs definitely increases the life of these heaters.  I can't complain though, it took about 10 years for mine to rust out.

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WingNut.  I had the Whale Seaward 6 Gallon Hot Water heater with Front Heat Exchanger.  The outer case is Galvanized steel, but it rusted out from the inside.  The outer case still looked fine.

 

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Look at Isotherm, more $$ but you get what you pay for. It heats up faster, stays hotter longer and uses half the power. About 700 watts, which is great when using the genset. 

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