Hot water heater problem?

[crieders]

I feel like I have asked this before (last season?); but here it is again.  The engine runs fine, hoses running into the hot water heater get hot but no hot water; a nice stream of water from the tap but alas not heated at all. 
Obviously the hot water is running thru the hot water heater well; its been burped, checked etc. The fresh water runs thru fine. Any thoughts or ideas? Toss out the old hot water heater (a pain to get out ) and start from scratch? Thanks

[Stu Jackson]

Cliff

How old is the heater?

Have you checked your ENGINE thermostat operation?

Are you absolutely sure there's nothing blocking the raw water to the heater?  I remember someone posting a picture of some long-ish hose that he found in one of the lines to the heater.  Are both the out and in heater hoses from the engine hot?

Just doing due diligence detective work here...

[Ron Hill]

Cliff : It sounds to me like you have a blockage in one of the lines or in the water heater itself. 
Those lines are for engine coolant - NOT raw water. 

[crieders]

both hoses to and from the water heater are hot. thats the mystery for me. I suppose I could remove the drain on the heater when the engine has been running for a while and see if hot water comes out. The heater is the original with a 1990 boat but fairly lightly used for what thats worth.

[Stu Jackson]

Ron's right, I mis-typed "raw" instead of fresh water.  Light use is not the issue, since the hot fresh water coolant is ALWAYS circulating through the heater.  I agree that it sounds like a heater problem if you're sure the water's getting there AND back.  If it was my boat I'd figure out a way to assure myself that there was actual FLOW through the heater.

[Ken Juul]

Is it possible that a PO disconnected the coolant lines from the water heater and joined them together?  You would get good flow, think it is burped, but no heat.

[tonywright]

This may be a silly question  but have you checked that the PO didn't do the following?

I remove the water supply from the back of the hot water tank each fall, and drain the HW tank. The two ends of the fresh water hose (input and output) are connected together so that I can pass plumbing antifreeze through all the system except the HW tank. When you turn on the faucet, water will flow out of the hot side of the faucet, but it is not passing through the HW tank at all, and so is cold, exactly as you describe.

This would have no impact on the hoses to and from the engine, also as you describe.

If this is the case, the fix is simple!

Tony

[crieders]

All the hoses are properly hooked up. I do the bypass in the winter also but I did hook up properly in the Spring. I will, however, check the hot water hoses again. Should I drain the tank of fresh water when the engine is hot to see if it is heating the water or is that a dangerous move? Thanks for all the suggestions.

[Jon Schneider]

Should I drain the tank of fresh water when the engine is hot to see if it is heating the water or is that a dangerous move?

Dangerous.  And what good would it do?

Look at both of Stu's posts.  He's giving you the likely cause.  You need to check to see that hot water is actually flowing through the engine return hose.  Does it feel hot?

Does the heater work on AC?

The heater itself has a thermostatic control for the AC operation.  I didn't think this had anything to do with the engine-circulated coolant since I believed it was electrically controlled (the hot water heater thermostat, that is) and simply turned on/off the electric heating element, but perhaps there's also a non-electric thermostat in the heater (separate from the one in the engine).  I'm just guessing.  Somebody here will know, or call Seaward.

[Ron Hill]

Cliff : Take off both of the heater hoses from the engine.  Then blow thru one and see it's free. 
The hoses go from the engine to the internal water heater coil with nothing in between and back to the engine.  If that's clear/free then make sure that the inlet from the thermostate and the outlet from the water pump are clear!!!!     

[crieders]

forgive my lack of knowledge but what would the engine thermostat have to do with it. The engine temp seems fine at 165-170 or so.

[Jon Schneider]

The coolant won't be circulating if the engine thermostat is closed.  If you're able to maintain 165 and not overheat, however, then you're right: your engine thermostat is working and coolant is at least flowing around the engine core.  Now the question is, is that coolant moving through the water heater hoses?

[pjcomeau]

Cliff,

Did you ever find out what was wrong? I'm investigating the same problem.

Thanks,

Pierre

[Allan.SVCarina]

Not sure if your problem is similar, but here goes.  I made a mistake  last year and put the hose connector on backwards, it seems it has a check valve in it so there is no backflow (only allows the water to flow one way).  I reversed and the water went through just fine.  It was one of those things that make you feel foolish, but I was glad that it was correctable with no cost except to my pride.

[crieders]

I replaced the  hot water heater and the thermostat and still the water does not get very hot. Last season, replaced the hoses. When I replaced the heater, I blew water thru etc to make sure of the flow. Its a real enigma