Hot water from engine

[Loon]

Wife complaining about shower water not hot enough while motoring. Usually the water is quite warm after 20 minutes. Considering the stb fresh water pump that's plumbed to the HWH however we have no increase in engine temp and it was replaced in 2009. Also no leakage or loss of coolant.
Any other ideas?
Thanks, Loon in the San Juans

 

[psneeld]

Blocked heat exchanger in hot water tank?

Any valves inadvertently turned off?

 

[Larry M]

Thermostat locked open? How hard are you running the engine? What does your engine temp gauge say?

 

[Edelweiss]

Wife complaining about shower water not hot enough while motoring. Usually the water is quite warm after 20 minutes. Considering the stb fresh water pump that's plumbed to the HWH however we have no increase in engine temp and it was replaced in 2009. Also no leakage or loss of coolant.
Any other ideas?
Thanks, Loon in the San Juans

Loon
Your post appears twice in two different topic areas, maybe a site Guru could combine them into one topic for you.
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Quote:
Originally Posted by Loon
Loon here. Cruising the San Juans and have a question. We developed a noise at 1500 rpms which went away at a lower rpm. A wife complained of lukewarm water while showering. I'm positing the fresh water pump is the culprit however no leakage. It is the 6.354M starboard engine,

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The impeller is metal and seldom fails, it's usually bearings that doom the pump. if the engine isn't running hot, fluid levels are normal and no leakage from the bearings....My guess would be it's something else.

I only had this happen once with my old hot water tank. Turned out to be a build up of "crud" at the engine hose bibs (where the heater hose from the tank connects to the engine) restricting the coolant flow to/from the water tank. Cleaned it out with a screw driver and battery brush. If you're at a dock where you can take the hoses loose and catch the coolant, you can check that out pretty easy.


PS: Also try blowing through the hose end to make sure there isn't a restriction in the water tanks heat exchanger.

The noise could be another issue that you might want to trouble shoot right away as well.

 

[Nomad Willy]

Just after we anchor up our water is too hot to do anything with. Only a 40hp engine heating it too.

 

[Keysdisease]

You got something wrong. HWH's that get exchange heat from engines make seriously hot water pretty damn fast. You got something going on there.

 

[cappy208]

Can you 'touch' the hoses going to and from the HWH? Are they warm? If they are hot then you may have scale in the HWH tank. Do you have a mixing valve in the system? Have you gone down and opened the valve ON the HWH?

Are there any other hot water valves that you can use that are NOT fed by the one your wife is using? Like an aft deck shower?

And as others asked, Is the engine water temperature at the normal temp?

 

[Baker]

Just an FYI...if HWH stands for "hot water heater", please refer to it as a water heater. If the water was already hot, then why would you need to heat it???....okay, as you were!!!!...

 

[BobH]

Some POs have installed mixing valves to keep unsuspecting guest from getting scalded. Trace the plumbing.

 

[cappy208]

@Baker: I'll tell that to my wife next time were shut down and she wants a hot shower from the hot water tank. With the engine off!!?

 

[BobH]

I think that 'hot water tank' is OK, just not 'hot water heater'.

 

[cappy208]

I think that 'hot water tank' is OK, just not 'hot water heater'.

On my boat the tank is used as both, a hot water tank when the engine is running, and a hot water heater when the gen is on, or on shore power. Same tank, two uses. I was just jumping on the generic term.


Speaking of hot water heaters, plumbed up to the engine cooling loop, has anyone ever lost a water heater (and the engine cooling water?) I was contemplating putting in a couple valves and a jumper valve to shut off that loop. Wondering how long water heater tanks last????

 

[Edelweiss]

I was contemplating putting in a couple valves and a jumper valve to shut off that loop. Wondering how long water heater tanks last????

It happens so rarely, its better to keep it simple: If you loose the hot water tank heat exchanger or split a heater hose, it's an easy fix to reconnect the good heater hose from the tank back to the inlet side on the engine to form a loop.

My last tank lasted 20+ years on this boat before the bottom rusted through. I have never lost the tank heat exchanger side of the circuit.

 

[BlueYonder]

There should be a shutoff where the hose is connected to the engine cooling system.

 

[siestakey]

Just an FYI...if HWH stands for "hot water heater", please refer to it as a water heater. If the water was already hot, then why would you need to heat it???....okay, as you were!!!!...

Baker your so wrong your right

 

[BruceK]

Baker your so wrong your right

Now that`s fixed, we can work on pronouncing "pedant". Most people say "ped-ant, but "P`Dant" is an option.

 

[Loon]

Water heat

Loon here, Thanks everyone, I think I have enough advice to last the weekend.

 

[Xsbank]

oh ok, I should read all the posts. Disregard.

 

[Peter B]

Loon, FWIW, when I had a similar issue, I found disconnecting the recirc hoses or pipes from the engine hose outlets that run to and through the hot water cylinder and giving them a good flush through from a hose flushed out a lot of built up crud, and then all worked well again.

 

[psneeld]

Forgot earlier...many tanks come with or had a mixing valve installed at some point.

May have to remove or figure out how to test it in place.

 

[folivier]

If the mixing valve is a Watts part of your yearly maintenance should be to turn the valve handle fully to both positions a couple times then return it to the normal position that you (hopefully) marked. I had these on the Aquahot on my RV and they occasionally will calcium up and start sticking. BTW the guts are replaceable in these. Just buy a new valve, remove the guts and install them in the valve.

 

[Loon]

Hot water

I think I'm going to try the low hanging fruit. First disconnect, clean hoses and connections and then back flush the tank heat exchanger. I'll try that and post a result. BTW we have no mixing valve. Loon

 

[FF]

I think I'm going to try the low hanging fruit. First disconnect, clean hoses and connections and then back flush the tank heat exchanger. I'll try that and post a result. BTW we have no mixing valve. Loon

These are on the antifreez loop in the engine.

Cleaning is usually not requirred

I would look for a kink in the hose circuit to the HW heater.

 

[Peter B]

I think I'm going to try the low hanging fruit. First disconnect, clean hoses and connections and then back flush the tank heat exchanger. I'll try that and post a result. BTW we have no mixing valve. Loon

Absolutely the right way to go in my experience. Worked for me, and I was able to stop there.

 

[cappy208]

I think I'm going to try the low hanging fruit. First disconnect, clean hoses and connections and then back flush the tank heat exchanger. I'll try that and post a result. BTW we have no mixing valve. Loon

Constant hot water likely leads to collapsed hoses. If the hoses aren't really hot leading to and from the HWH then I would suspect a collapsed kinked hose. Are they soft? The hot water from the engine should have antifreeze in it. This has anti corrosion inhibitors. The engine side of this loop should be fine corrosion wise. Calcium build up would possibly be on the actual freshwater side INside the HWH. If the engine coolant is flowing freely then I would suspect your HWH needs de scaling. Vinegar, and a couple hours.

You never responded (that I caught); Is the engine running at normal temps when hot? A broken thermostat on the coolant side could allow the water to not get as warm as it used to, mimicking the low temp issue in the HWH. Thermostats break Open when they break. Letting more unrestricted cooling water into the system.

 

[psneeld]

I am not sure if the kind of engine(s) have been mentioned.

If saltwater cooled...plugging is very common...but I agree not for those in a coolant loop unless the engine sat for a long period of time and a lot of rust built up. Or as some post, the antifreeze has gelled from mixing different kinds.

Checking for flow will eliminate clogging or clasped hose issues unless using a lot of pressure.

 

[cappy208]

Gotta be honest. The old salt water cooled engines never even entered my mind. I would have thought in this modern day and age....... Well, Look at Washington.

 

[Loon]

This Perkins 6cyl is 1982 vintage uses an antifreeze loop w/ no mixing valve. The engine has always run at the same temperature 185 degrees F. There are very short runs to and from the engine and do not appear misshapen in any way. I suppose the is a calcification possibly in the HWT since the venerable gentleman we bought it from used it very little for the three years previous. What is the easiest way to introduce vinegar or descaler into the HWH?

 

[cappy208]

As long as both hoses are HOT to the touch, then it would appear the HWH is cruddedup. here is a visual of how I cleaned mine, as well as the Renai hot water heater in my house. Works just fine, and only takes about 15 minutes (after setup) to get done.
And, you can shop for the cheapest, gallon jug-o-vinegar at any store. Doesn't have to be brand name.

I had to rinse my entire system this spring, because all the calcium had broken loose and was clogging each and every faucet on boat. If I had my druthers, I would have liked to cleaned the HWH tank, and kept the crud out of the lines and faucets. Live and learn!

 

[cappy208]

This Perkins 6cyl is 1982 vintage uses an antifreeze loop w/ no mixing valve.

The mentioned mixing valve (Tempering valve) would be installed on the Potable side, not on the engine side. It could be a simple valve which interconnects between the hot and cold supply line anywhere from the HWtank to the first faucet.

To be honest, I haven't seen many boats with them installed. (even my 120' tugboat!) Hot water is HOT.