Hot Water Heater - but no hot water now

[Phr3d]

Backstory:

It worked fine. I have fantastic memories of feeling clean after a hot shower on the boat.

- boat yard replaced exhaust system (waste tank and water heater removed) and elbow including a new fancy Forespar vented loop.
- flushed/changed coolant when new thermostat housing for alternator mount installed (long story, see other thread).

We went to Catalina. No hot water. Burped cooling system. No hot water.

Now wondering what I did wrong - but since I'm not the only guy who was in there, wondering if connections at the water heater reversed is a maybe? Thermostat stuck? Or, is it as simple as something clogged as it sat for several months...

Advice on where to start looking?

 

[bsangs]

Is the hot water not working from engine heating AND from the breaker panel? The reason I ask is this. I replaced my hot water heater this offseason. It immediately worked from the breaker panel, but my first time out, it did not appear to be working from the engine heating. The second time out, it did, even though I didn't do anything to it between the two trips.

And this may seem rudimentary, but are you certain the input and output hoses for the hot water heater are open? When I first got the boat years ago, there was no hot water, but it was because the previous owner had drained the tank and the input/output hose valves were in the closed position, and I knew nothing about the system at that time. Good luck with the diagnosis.

 

[Prairie Schooner]

Also, Paul, can you explain what you mean by "waste tank and water heater removed"? Do you mean they were removed to do the work, but put back in? And by "waste tank", do you mean the coolant overflow tank?

 

[JSM]

Also, Paul, can you explain what you mean by "waste tank and water heater removed"? Do you mean they were removed to do the work, but put back in? And by "waste tank", do you mean the coolant overflow tank?

The muffler on the 34-2 is buried behind the water heater and waste (black water) tank in the starboard lazarette. Both tanks need to come out to get to the muffler.

 

[JSM]

No hot water. Burped cooling system. No hot water.

Did the water heater get refilled after it was reinstalled? Turn on the hot water faucet in your galley and let the pump run. This will draw water from the storage tank to the water heater and fill it. Once its full water will spurt out the faucet. I go thru this every spring after de winiterizing the system.
On my 34-2 there is a bleed valve on the hose running from the engine back to the water heater. Open it while the engine is running to bleed any air from the system.

 

[Christian Williams]

On some boats the water heater can be isolated from the hot coolant circulation by in-line valves. Check for any such valves.

 

[Phr3d]

hot water faucet in your galley and let the pump run

yes - looked in owners manual which says to run hot and cold in galley then repeat in head

while the engine is running to bleed any air from the system.

yes to this as well - squeezed hoses to break loose any stuck bubbles also

 

[Phr3d]

are you certain the input and output hoses for the hot water heater are open?

I can try to verify this - what do I look for and where?

 

[Phr3d]

Also, Paul, can you explain what you mean by "waste tank and water heater removed"? Do you mean they were removed to do the work, but put back in? And by "waste tank", do you mean the coolant overflow tank?

John answered this really well with the word "buried". They were put back in ... but hoses could have been mixed. The manual doesn't seem to care about the hoses from the engine, but makes a point of cold vs hot on the fresh water side.

 

[Phr3d]

Is the hot water not working from engine heating AND from the breaker panel?

I will have to verify this. I started to check it but didn't wait very long with water running. About how long does the heater take to heat the water? And, about how long for hot water to get to the galley (or head)?

 

[Phr3d]

On some boats the water heater can be isolated from the hot coolant circulation by in-line valves. Check for any such valves.

I didn't see any valves other than the drain valve and the T&P valve on the heater itself. What do these valves affect anyway? The fresh side or the coolant side?

 

[Loren Beach]

It might have been different on our former M25XP, but it came with two itty bitty brass valves on little brass(bronze) T's, just above the thermostat housing. This was where the two hoses started, that went out of the engine compartment to the water heater coil connections.

 

[bsangs]

I can try to verify this - what do I look for and where?

Wish I had a picture for you. With mine, there are valves on the hoses that lead to and from the hot water heater. Mine are located under the cockpit, where the hot water heater is. I assume it's similar on your 34-2. Just a small, metal valve that, just like a seacock, controls the water flow. Also, as a previous poster mentioned, make sure the hot water heater is actually filled. DO NOT turn on the water heater breaker switch until you're sure of that.

 

[Christian Williams]

What do these valves affect anyway?

If you have them, they are merely to stop the flow of (hot) coolant from going through the water heater, and therefore isolate it from the cooling system.. That might be useful when changing engine coolant, or if there were a leak in the water heater, or for (cockamamie) theories that engine overheating is linked to the water heater sharing engine coolant.

As a side note, it does take quite a while for my engine to heat up drinking water. At least half an hour, more like many hours. Many heaters also have an electric heating function when on shore power. On most of our old boats, that probably is no longer functional, but to work only needs the electric heating element to be changed out.

 

[Phr3d]

It might have been different on our former M25XP, but it came with two itty bitty brass valves on little brass(bronze) T's, just above the thermostat housing. This was where the two hoses started, that went out of the engine compartment to the water heater coil connections.

This is more of an FYI:

While this is not my engine, it is so close - even to the valve in the thermostat hose.

 

[Captain Pete]

I share your frustration. I am struggling with the same problem on my 35-3, which has a yanmar 3GM30F that was disconnected from the water heater when i got the boat and had a loop on that above the thermostat "in and out" you show .

As far as i can tell (and i could be wrong) the blue black hose you show is the hot coolant going out to the water heater.

The black hose would be the coolant return from the water heater.

Below is a pic of my water heater and from what i can tell looking at the water heater manual the black hose on the upper right is the coolant from the engine going into the water heater. The black hose on the lower left is the return back to the engine.

It took me a while and repeated trial and error to figure it out (and i am still not sure...), especially the correct out to and in from the engine hose configuration. But hooking it up and running the engine i had no joy and no hot water.

Thinking maybe there needed to be a vent in the connections to ensure no air in the lines I have now hooked up to an existing expansion tank high up in the cockpit locker by the trash bin (seen below) that was there presumably from when the boat had its original universal diesel and will see if that works (i did not have time to run the enging long enough to know if anything heated up).

It is a frustrating exercise requiring too much time in the locker and on hands and knees and putting lots of money in the swear jar.

 

[Christian Williams]

What helped me in a cooling system puzzle was to stop thinking (which had not helped) and go direct to making a mess.

in this case it would be to disconnect the water heater coolant outflow hose, hold a bucket under it, and have somebody start the engine. Coolant should flow into the bucket.

If no flow, switch to inflow water heater hose. If no flow there either, problem is higher upstream. If coolant flows into the heater, but not out, the heater itself is clogged.

Probably not how a boat mechanic would do it, but does provide indisputable evidence.

 

[Loren Beach]

Probably not how a boat mechanic would do it, but does provide indisputable evidence.

A wise mechanic, now long retired, used to advise me to do something similar when trouble shooting. i.e. start at one end of the problem, and methodically work back, fitting by fitting, hose by hose.

 

[Phr3d]

I found this diagram in the Yanmar Service Manual.

I'll be going to the boat tomorrow with buckets, hoses and so on...

 

[Second Star]

If the yard replaced hoses they may have erred. If the HW heater was supplied engine coolant from the discharge side of the engine heat exchanger the coolant wouldn't be very hot. A hose run like that might have been "easier" for the mechanic that the previous hose run that worked.