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Wally-1840
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Joined: 11/9/09
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Water heater

hi all,
well, we need a new water heater. Looks like a pretty straightforward job. My question is what is the best way to refill the antifreeze side of the unit to prevent an air block?

Wally
"Onanne"
2000 MKII, deep keel, tall rig
​Lake Champlain
 

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Haro
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I just replaced my water heater. I mixed 50/50 distilled water with antifreeze in a water bottle and poured into the hose at the engine side using a funnel. At the return hose near the engine side I placed a foot pump that is used to inflate small toy inflatables and sucked air out while I poured in the fluid. At some point the fluid will squirt out of the pump. This means you have filled the hoses and the water heater coil. For me it took 22 Oz of fluid.
Be sure to fill the reservoir as well before starting engine to avoid introducing air into the engine.

Wally-1840
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Perfect! Just the info I was looking for! Thanks very much.

Got the old one out today in just over an hour. New one is being delivered Monday.

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Haro
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I had noticed that I was loosing antifreeze and having to add a few ounces each month, but had not been able to to locate the where I was loosing it. Quite accedently I noticed the cristal residue that indicated the loss of fluid. 
Since the replacement of the water heater there has been no loss of fluid.
Visist Here to learn more

Here are photos of my installation. The hoses were 11' 8" and 11' 1' to the back of the heater.

Does anyone know what the pupose of this device is that is located on the cold water input side of the water heater?

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LeslieTroyer
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The last photo the square is a pressure regulator.
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Haro
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Thanks, Les

Wally-1840
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Posts: 117

Hi,
Thanks for the detailed reply. A couple of questions. 1. Are your new hoses automotive? 
2. Are there any special “tricks” to get them from the engine to the water heater?

As for the device, I’ve always assumed it’s a check valve to keep hot water from rising into the cold.
Thanks again, you’ve helped greatly!
Wally

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Haro
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The hoses are special, hardwall marine wet exhaust hose. That means it has spiral spring in it and resists up to 250F heat. I paid about $200.00 for 24 feet of hose.

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LeslieTroyer
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It may also be a check valve. I have one on the pressure water input from the dock ( great method for sinking a boat if faucet is left on).
Wally-1840
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Sorry, another question. I didn’t pay much attention to which hose came off the back of the heater when I disconnected. From your pictures, is the hose labeled “long” the one that goes outboard?

i hate when I’m dumb!
W

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Haro
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Yes, the one labeled long is the one that is connected to the far side of the heater coil, near the hull, hence longer hose is needed. I marked them before removing in case the direction of flow makes a difference.

Wally-1840
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Done. 3.5 hours total; removal, install and test. Thanks for all your help!
Wally

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LeslieTroyer
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According to that it is the input alternator excite line - it powers the regulator. I hope you’ve moved the B or B+ (orange) alternator output to either the starter solenoid or back to the house battery. That drawing is for the M25. The M25XPB is a bit different. Colors of the older engines can be almost anything - which is why the terminal it’s attached to is important. If you have no power to the switch trace back till you find power. Find or draw a diagram that represents your engine!!! Les
stephenemmerman
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Joined: 12/22/07
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Have a overheating problem on my Yanmar new 7 years ago. I think it is the hoses going to the hot water heater. I will try your method mentioned here. I also own a 380 in NY. This boat has a some type of valve between the engine and the hot water heater to solve the air in the line problem. Does anybody have a similar valve and where I can get it. I just replaced my heat exchanger in the Yanmar for $3200 part cost. So I know it is not the heat exchanger. I use a laser tool I got at harbor Freight it works great. Put a new thermostat and heat sensor in. All new hoses on hot water heater from engine. Thanks in advance. i am tired getting towed in from Boat Us. Weather is warm in florida and the pool is 86. The boat sits behind the house in Punta Gorda Fl. Time to jump in the pool and do my 30 laps. 

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