Replacing water heater, advice on brands?

YeOldeStonecat

YeOldeStonecat

Active Member
Jun 10, 2018
332
Waterford, CT, boat in Deep River, CT
Boat Info
'97 300 DA "Me-Shell"
Engines
Twin 5.7 V-Drive
Believe the existing HWH in our "new to us" '97 300da is original. Atwood MPD 93757/model EHM6-SM
Barely gives us warm water for maybe 20-30 seconds. Plus any water coming out of it stinks like the biggest batch of rotten eggs. Have run bleach through, have run hot water many times, just get the smell out but the fact that it's barely warm for 30 seconds makes me think she's a goner

See enclosed pics. Appears they built the boat around the HWH so I'll have to remove risers/exhaust/heat exchanger and who knows what else just to get it out and a new one in.
Plus prior owners/mechanics appears to use it as a step stool. Concerns me.

Advice from the collective braintrust here at CSR...? Worth trying to replace parts? Or replace whole unit?

H2OHeater1.jpg
H2OHeater2.jpg
 
Well....something is wrong with it. That garden hose is a bypass which should not be there. If you want to see if the hot water heater works, remove the bypass and cap off the connections with standard garden hose caps.

Then you will be running water through the hot water heater. The hot water heater has two sources of heat: electric and coolant from an engine. In either case, you will find out pretty quickly if the hot water heater is usable. Be prepared that the hot water will stink for a while until it is flushed out.
 
In response to your replacement question.....for the most part these things are replaced given how much work it takes to access them. Yours has had a 20+ year service life which is double what they normally get. The work itself to replace the unit is relatively easy.....getting to it is the issue.

I would remove the bypass, flush the heater and switch it on. It may work or the heat you might have felt came from the heat exchanger from running the engine. If it doesn't heat up in 15 minutes.....the electric heating element is probably not working.
 
Thanks for the replies...
I saw that light colored hose and thought to myself...crossover, cancelling out? So why would the prior owner put that there? If the hot water heater died...why put a bypass there if all you need to do is simply turn on the cold water faucet?

Does Atwood make good HWHs? Or better brands to recommend? We will likely upgrade to a larger boat within 5 years. Don't want cheapest route but no need to install a "best of the best of the best" since won't get all that money back on resale.
 
Doing some Google-Fu here...it seems that HWHs with aluminum tanks are more prone to the "stunk odor" water, and it's better to get SS tanks, or ceramic lined.
Looking at the IsoTemp SPQ-25 model, a 6 gallon with SS inner tank
Noting it also comes with a crossover hose..but appears a safety feature. 750 watt unit
https://www.defender.com/product.js...-gallon&path=-1|51|2234308|2234311&id=2357713

So long as it measures to fit in there roughly where my current one is...I'll measure to make sure the 26" length of the IsoTemp 25 model will fit without cramping stuff in there like the rudder steering mechanism.
 
That "white" hose is a bypass arrangement, with valves. Camco makes them, I installed one on my HWH this year. It is an easy way to winterize the water heater without filling it up with 6 gallons of anti-freeze.

Did you check to see if the bypass is "open" (meaning that water is NOT going to the water heater) or "closed" (water IS going to the heater)?

You said it gives hot water for a few seconds, that could just be the conductive heating of the water in the lines. You could see if your water heater is full by opening the drain valve a bit. Careful for hot water. Also, be careful not to drain the heater "tank".

Jaybeaux
 
Jaybeaux said:
That "white" hose is a bypass arrangement, with valves. Camco makes them, I installed one on my HWH this year. It is an easy way to winterize the water heater without filling it up with 6 gallons of anti-freeze.

Did you check to see if the bypass is "open" (meaning that water is NOT going to the water heater) or "closed" (water IS going to the heater)?

You said it gives hot water for a few seconds, that could just be the conductive heating of the water in the lines. You could see if your water heater is full by opening the drain valve a bit. Careful for hot water. Also, be careful not to drain the heater "tank".

Jaybeaux
Click to expand...
Nailed it. Plus one on the hose.
 
Yup....I agree....I just didn't see a valve on the plastic fitting. Also, I thought the Camco kit had two brass fittings.
 
There are a few CSR threads on replacing your hot water heater. I wouldn't go with anything exotic....your Atwood lasted 20 years which is a lot longer than you plan on keeping the boat. I replaced mine with a Kuuma which is identical to an Atwood for a fraction of the cost (they look suspiciously like the West Marine brand down to the blue plastic cover wrap on the aluminum). While folks will say it is made in China.....what isn't? Even Atwood makes a number of their heaters in China.
 
I would connect a hose to the heaters pressure relief and run it over board...... and then connect your boat to a water supply and let it flush itself for a good while.

Remove the jumper hose and cap and give the HW tank another try.

If you are adventurous you could disconnect the IN hose and the Out hose from the unit and then connect some garden hose and use a higher % of bleach solution and flush it out directly w/o bleaching your entire system.
 
YeOldeStonecat said:
Isotemp Basic 24 model...seems similar specs as far as size/power, but shorter and wider...yet ~200 more
https://www.defender.com/product.js...-gallon&path=-1|51|2234308|2234311&id=2355931

Wonder what big differences are for my situation.
Click to expand...
I installed an Isotemp Spa a few years ago and have been very happy with it. My tank location is pretty much inaccessible and impossible to get at for flushing or anything else. So, I wanted the stainless tank as I had been plagued by the "smells". The Isotemps have a mixing valve so the heater runs at a relatively high temp but the output is combined with cold to deliver a safe temp at the shower/faucet. This also provides a bonus of effectively increasing the amount of hot water you can use from the same sized tank. The only difference between the "Basic" and "Spa" models is that the outside is poly on the Spa and stainless on the Basic; insides including the stainless tank are the same.
 
YeOldeStonecat said:
I must me over tired and brain farting...how does that "valve" on the right side (the blue line) help in winterizing and minimizing antifreeze?
Click to expand...

if you are talking the valve with the little metal handle that is not connected to anything.

It's the pressure relief valve just like your home water heater.

I see no other valve in your picture so the little cross over line is confusing.
 
So, to weld or not. I heard my water pump hitting every 10 minutes or so. A bit of investigation and I found the leak where my Atwood stainless tank is welded to the stainless pressure relief.

Looks to me like a good candidate for a tig, but for $300 should i just replace it. Works fine otherwise, and it looks like a PITA to remove.

To weld Id cut the white case and bend it back to make room to access the weld. The bend back and spot weld it.

Pic attached.
 

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My vote for a 21 year old water heater failing at the end of the season: Replace it over the winter.
 
The valve that is on the right side(blue hose) next to the tank (with the white hose tee on it) this is a bypass valve. In one position it lets water into the water heater tank- in the other position it bypasses the tank and sends the water into the white hose where it then goes into the tee on the left and then out to the boat faucets.
It appears that it is still in the bypass position.
 
Well, mine looked new compared to that, and worked fine except for a leak on the weld of the pressure relief. 2 hours with a welder got it down to a drip, the water pump now fires every 30 minutes instead of 10 minutes. But it does need to be replaced or bypassed. Not sure how to bypass it and if its safe with the hoses going to the port engine. I can live with it for the next 4 weeks as is. I don't want to pay to winterize a unit that I'll replace in the Spring though. The last I heard it was about $950 to have the shop change it out.

I can do it myself if I can get to it. It's 13" tall and I have 11 inches between the top of the engine and the deck. My vacuflush system would have to be removed, and the port hatch hydraulic quick release pulled. Or maybe the oil filter and fluid reservoir on the port engine instead of the vacuflush.

Grr. 3 Weeks of ownership and now I'm a full time mechanic.
 
Didn't mean to hijack your thread. For $350 it's about as cheap as a boat part gets. The labor is significant if you have to pay. For you since you have to remove it to work on it, just replace it. The welder said he could spend a few more hours working on the one fitting, but he suspects corrosion inside as well and recommended we call it quits and I replace it.
 
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