400DA Hot Water Heater Replacement - How did you do it?

Boat Guy

Well-Known Member
May 15, 2013
2,289
Who knows? Could be Cali, Oahu, Florida, Annapolis
Boat Info
400 DA
Engines
CAT 3116s
I tried to search the posts to find some answers but came up short.

I have the Atwood EHM11. It's an 11 Gal. hot water heater. I think it was an option on the 1997. Anyway, it's positioned aft of the Westerbeke 7.6 Generator on the Starboard side. I can't figure out how to get it out in one piece and even if I did disassemble it someway, I'm not sure how to get the replacement in...

Has anyone done a direct replacement or did you have to come up with a different solution? Ideally, I'd like to just do a swap-out without having to take the whole boat apart... Too much to ask?
 
I think I've read on here somewhere that it can be moved behind the engine and removed out between the engines. Gonna need a small mechanic or two.
 
I think I've read on here somewhere that it can be moved behind the engine and removed out between the engines. Gonna need a small mechanic or two.
I have the same boat and I am sure I will have the same issue soon. What if you were to actually cut it up into smaller pieces , remove it and then install a on demand water heater instead.
 
I have the same boat and I am sure I will have the same issue soon. What if you were to actually cut it up into smaller pieces , remove it and then install a on demand water heater instead.

Might not matter to everyone but keep in mind with the on demand heaters you would always need power applied to get hot water. We find that if I bring the HW tank up to temperature and full before leaving the dock for day trips that there is no need to run the genset for just washing hands, quick dishes, etc. If you run the genset all the time that likely won't matter, but ours is noisy so I only start it when I really need it.

Would be nice to get some space back in the bilge with an on demand heater as well as the unlimited supply of water for a shower.
 
UPDATE:

Re on demand systems....I've heard they draw a lot of amps and I didn't want that load on the systems...

For me, I was very happy with the 11gal HWH until it had a leak and wanted to replace with a similar model.

The difficulty, as everyone knows, is location and being able to install the new one. The old one can be cut out, so it's not really a problem to remove...

I could not find a way to install the new HWH, which is basically a 16.5" square box, without having to do either move the engine or cut the fiberglass deck.

So, with the suggestion of another 400DA owner that already did it, I decided to place the unit between the engines as forward as possible just before the drop down for the forward bilge pump.

It fit right in and I pulled the electrical out of the loom and reran it through the conduit on the firewall. I used the same openings in the waterlines and just ran longer lines to the hot and cold side. I did go and get new fittings for the HWH just to be safe....

All was done in about 4 hours...
 
image.jpeg
It makes a great step but the outer shell is thin and does bend a little. I bent up an aluminum diamond plate cover to solve that issue.
 

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Creative and Smart!
 
UPDATE:

Re on demand systems....I've heard they draw a lot of amps and I didn't want that load on the systems...

For me, I was very happy with the 11gal HWH until it had a leak and wanted to replace with a similar model.

The difficulty, as everyone knows, is location and being able to install the new one. The old one can be cut out, so it's not really a problem to remove...

I could not find a way to install the new HWH, which is basically a 16.5" square box, without having to do either move the engine or cut the fiberglass deck.

So, with the suggestion of another 400DA owner that already did it, I decided to place the unit between the engines as forward as possible just before the drop down for the forward bilge pump.

It fit right in and I pulled the electrical out of the loom and reran it through the conduit on the firewall. I used the same openings in the waterlines and just ran longer lines to the hot and cold side. I did go and get new fittings for the HWH just to be safe....

All was done in about 4 hours...
 
.........and then install a on demand water heater instead.

In the spirit of portable gasoline generators on swim platforms and bows, I’d like to raise caution about installing non-marinized household appliances in boats. Please make sure you only install appliances that are appropriate for boat/marine use so no one dies from electrocution.
 
In the spirit of portable gasoline generators on swim platforms and bows, I’d like to raise caution about installing non-marinized household appliances in boats. Please make sure you only install appliances that are appropriate for boat/marine use so no one dies from electrocution.

And rated for a fume/engine room environment.
 
Yes, excellent point. My mind was in diesel land, but definitely another great point of caution to those with gas powered boats.
 

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