The hot water heater on my boat isn't working off the engine. It does work off the AC panel while on shore hook-up. There are two hoses that come off the engine and go to the hot water heater. While running the engine I checked them. One is hot which I assume is due to the water coolant passing thru. When I checked the other end of this hose as it enters the hot water heater it is no longer hot to touch. Could it be clogged? The second hose off the engine is cool and also cool at the hot water heater. I need some suggestions as to what the problem may be. Could the hose be clogged? Why isn't the one hose hot all the way to the hot water heater? Why is the other hose cool to the touch. How does this whole thing work? Any help is appreciated. Thanks. Joe Mullee
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Al M
Your heat exchanger coil in the heater is probably
Clogged. An easy test would be to remove the colder of the two hoses and start the engine to see how much flow you have. Compare this with how much flow goes in from the other hose. Some installations only let water circulate after the thermostat opens while others may use a restrictor and actually reverse the flow when the thermostat opens. The temp of the hoses should be close to identical if the coil inside is flowing OK. If the boat is raw water cooled and the heater is more than say 5 or 6 years old it's a good bet the exchanger is shot. Or at least mine was.
Clogged. An easy test would be to remove the colder of the two hoses and start the engine to see how much flow you have. Compare this with how much flow goes in from the other hose. Some installations only let water circulate after the thermostat opens while others may use a restrictor and actually reverse the flow when the thermostat opens. The temp of the hoses should be close to identical if the coil inside is flowing OK. If the boat is raw water cooled and the heater is more than say 5 or 6 years old it's a good bet the exchanger is shot. Or at least mine was.
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Joe Mullee
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Al M
At the heater.
All the usual caveats about spillage and scalding. If you removde the hose at the heater you shold have the same flow out of the hose into the heater as the hose out of the heater. They should also be about the same temperature. Alternatively you could try running a hose into the heater from a pressure water source(dock hose or pressure water) and see how much flow it has or has not. There shouldn't be any noticable restriction. Al
All the usual caveats about spillage and scalding. If you removde the hose at the heater you shold have the same flow out of the hose into the heater as the hose out of the heater. They should also be about the same temperature. Alternatively you could try running a hose into the heater from a pressure water source(dock hose or pressure water) and see how much flow it has or has not. There shouldn't be any noticable restriction. Al
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Jon
There could be an "air lock" in the loop
from your engine, to heater, and return. If the air bubble is out of the line, when the engine is at operating temperature, both engine coolant hoses (the "In" and the "Out") at the water heater should be hot, or very warm to the touch. Make sure that your engine coolant is filled to spec. level. Then try running engine (at the dock) with the engine coolant filler cap off until engine heats up. IF, AS THE ENGINE HEATS UP, THE COOLANT EXPANDS AND APPROACHS OVERFLOW; SHUT DOWN ENGINE. If while running the engine, the coolant level drops noticably, you've successfully "bled" the air bubble out of the line. If it didn't drop. Leave the cap off and shut down the engine. As it cools, the bubble might be drawn out. (Again, there would be a drop in the level of coolant.) Your closed loop engine cooling system should have a coolant overflow tube (in case that the coolant is overfilled). If neither of the above successfully gets the air bubble out of the line, with a cool engine, you might try filling the engine coolant to the brim, PUT THE FILLER CAP ON and run the engine again. Be ready to catch any coolant overflow as the engine heats up. If none of the above gets the air bubble out of the line, you'll have to disconnect the return line from the heater to the engine, and manually fill it with coolant to drive the air bubble to the surface.
from your engine, to heater, and return. If the air bubble is out of the line, when the engine is at operating temperature, both engine coolant hoses (the "In" and the "Out") at the water heater should be hot, or very warm to the touch. Make sure that your engine coolant is filled to spec. level. Then try running engine (at the dock) with the engine coolant filler cap off until engine heats up. IF, AS THE ENGINE HEATS UP, THE COOLANT EXPANDS AND APPROACHS OVERFLOW; SHUT DOWN ENGINE. If while running the engine, the coolant level drops noticably, you've successfully "bled" the air bubble out of the line. If it didn't drop. Leave the cap off and shut down the engine. As it cools, the bubble might be drawn out. (Again, there would be a drop in the level of coolant.) Your closed loop engine cooling system should have a coolant overflow tube (in case that the coolant is overfilled). If neither of the above successfully gets the air bubble out of the line, with a cool engine, you might try filling the engine coolant to the brim, PUT THE FILLER CAP ON and run the engine again. Be ready to catch any coolant overflow as the engine heats up. If none of the above gets the air bubble out of the line, you'll have to disconnect the return line from the heater to the engine, and manually fill it with coolant to drive the air bubble to the surface.
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WildBill
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Ed Ryan
One more option to solve air lock
I agree with the options that Jon offered and offer one more. At the input connection to the water heater (from the engine) there is sometimes a petcock installed that allows you to bleed the air out of that part of the system. With the engine running, open the petcock slightly until coolant comes out, then close it. That was what did it for me when I had a similar problem after replacing the coolant hoses from the engine to the water heater.
I agree with the options that Jon offered and offer one more. At the input connection to the water heater (from the engine) there is sometimes a petcock installed that allows you to bleed the air out of that part of the system. With the engine running, open the petcock slightly until coolant comes out, then close it. That was what did it for me when I had a similar problem after replacing the coolant hoses from the engine to the water heater.
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