Water heater replacement, Atwood or Kuuma?

[pablosgirl]

While on the boat this week I noticed that the bilge pump was cycling and so was the pressure water pump. So the original Atwood water heater is shot.  Some online shopping shows that I can get the Kuuma 11812 from Hodges Marine for $297.05 and the Atwood marine S600 from Boat & RV Accessories for$385.09.  Both have the same dimensions with the rear heat exchanger connections.  Does anyone have any experience with either of these.  I am inclined to go with the Atwood since the original lasted this long. Does anyone have the Kuuma model and was it a drop in replacement.

[waughoo]

I have the Kuuma, but it came with the boat.  I have no knowledge of how old it is.

[scgunner]

Paul,

I'm impressed it's lasted this long my original rusted through about 20 years ago. It was a regular non-marine RV unit. I replaced it with a marine unit with a square S/S case which fit the space and worked fine until I took it out of line when I installed a flash heater.

[Ron Hill]

Paul : I found that the galvanized outside does the job. If you use Stainless (more $$) you don't gain much because they all have the same insides (NOT stainless)!!

A few thoughts

[Jeff Tancock]

Check all your fittings. I thought mine was shot but on examination it was just the plastic hot water out elbow fitting that was leaking. Had to replace with a brass fitting as that was all I could find on a remote island.
Lucky.....A $10 solution!

[Ron Hill]

Guys : I replaced the both the inlet and outlet with brass fittings.  I found that the outlet got very HOT because it transmitted the heat from inside. I changed the outlet elbow back to nylon.

A thought

[pablosgirl]

Hi Jeff ,

Thanks for the tip about the fittings.  I had already checked them. Also there was a pretty obvious stream of water flowing out between the bottom of the water heater and the plywood shelf. In addition the whole bottom of the outer case was pretty rusted. I think I got my moneys worth from it. I am now hoping for a Black Friday sale on marine water heaters. 

[Jim Hardesty]

When replacing the water heater consider adding a by pass.  Even if you don't need to winterize it may be worth the few extra bucks.
Jim
https://www.westmarine.com/camco-water-heater-bypass-winterizing-kit-329195.html?utm_source=pepperjam&utm_medium=affiliate&utm_campaign=159404&utm_content=4923727131&clickId=4923727131&cm_mmc=AF-_-Pepperjam-_-159404-_-4923727131

[pablosgirl]

I bypassed the hot water heater until I get a new one with a 1/2" nylon splice connector from WM. The bypass is a good idea but I live on the Texas gulf coast and I don't think it is worth the effort for me.  I will be replacing the hoses to the engine.

[Noah]

Two "upgrades" I did on my fresh hot water system.
1. Added a temperature mix valve, to better regulate how hot the water is coming out of the tank.

2. Re-plumbed the hot output side with PEX A tubing to both sinks, which is better suited to carry high temperature water than original vinyl fresh water hose.

[pablosgirl]

Installation Report

I decided to go with the Kuuma.  Being less expensive, that helped to offset the cost of the replacement heat exchanger hose. With tax, 14' of Shields 250 hose was $117.62 from go2marine.com.

Lessons learned from installing the water heater

1. You have to remove the water heater access door and frame.  The water heater is 13" high by 13" wide. The rough opening in the sink cabinet is 14" wide which is needed to get the water heater under the sink. I also removed the drawer and frame that my boat has under the sink.

2. The heat exchanger inlet and outlet nipples are 1 1/16" lower in the rear panel of the Kuuma water heater. What this means is that the inlet and outlet nipples are in line with the shelf that the fresh water pump and the icebox drain foot pump are mounted on.  If I had known that I might have gone with the Atwood unit.  My solution was to fix two 13.5" x 19" pieces of 5/8" plywood atop the existing water heater shelf. This provides enough clearance above the water pump shelf for the forward heat exchanger nipple and hose to the engine.

3. I replaced the hoses even though they looked in really good shape.  They were marked with "marine water hose".  After What I believe is 36 years of service, it was time.  I did periodically inspect them though and planed on replacing them when the water heater failed.

4. Now is a great time to clean this area of the bilge!  With the water heater out of the way, you have pretty good access to the bilge area from the sink cabinet to the engine. I found two missing bottles of hand cleaner and one of dish soap the fell off the water pump shelf in addition to an assortment of other items.

5. Also, with the water heater out you have access to to the sink drain and fresh water hoses.  I replaced a few of the rusty hose clamps.

6. Need replacement teak plugs for reinstalling the water heater door frame and under sink shelf frame.

7. Install the replacement hose starting in the engine bay.  I found that I could easily push the hoses in by angling the hose aft. They will slide easily along the hull. Start with the aft hole then the forward one. Note the hose routing around the pump shelf before disconnecting the old hoses so you can install the new ones the same way.