Water heater only luke warm from engine heat.

[donvanv]

I'm afraid I am just a little delinquent following up on this, but I want to add that problem has been solved.
I removed the valve shown in original photo and connected the two hoses directly in the conventional manor. Now get much hotter water. It seems that valve was only a bleed valve and still not sure if it was the culprit. It was also necessary for me to drain and replace coolant, so that may have also contributed to the fix.
Thanks all for contributing.
Don

 

[Gunni]

As ThinWater notes if your engine coolant is Ethylene Glycol and your water heater coil bursts you will be putting poisonous antifreeze into your potable water circuit. For that reason I changed out to one of the new diesel engine Propylene Glycol coolants (Fleetguard). Non-toxic.

 

[donvanv]

Good to know Gunni. Thanks

 

[NYSail]

My Pearson with a 3hm35f will heat the hot water completely in a 10/15 minute ride from slip to mooring. Raritan unit 6 gallon.

 

[jssailem]

Could this be limiting the volume of hot engine coolant going through? See photo

The image is not showing enough of the front to identify the valves , inlets and outlets on the heater. Need full frontal image. The units come in several configurations. Electrical only, Heat Exchanger only and combination. Need to see the complete front, otherwise it is guessing.

From your description possibilities exist:

1. Coolant lines blocked,
2. Not engine heat model,
3. Blockage in WH heat exchanger
4. Plumbed wrong
5. Valve partially closed (Not the one in image)

The valve in the image appears to be a mixing valve. Trace the hoses. It is a mixing valve if both cold water line from water tank and line to your hot water boat supply are attached.

 

[SycloneDriver]

My B First285 has a very similar hot water setup. The T-valve is at the high point and apears to be used to blead air from the system.

The water gets hot fast enough.

I sail mine all the time in the winter with the tank empty and have not damage the heat exchanger.

 

[MitchM]

i agree with online lee. having spent a large part of my youth as a chemical engineer doing heat transfer calculations, i can see that if one is offshore, and runs a heating loop of stainless steel carrying 200 degree engine antifreeze through a water tank that's empty of water, heat tenser happens. , there is heat transferred from the hot hose loop to the air inside the tank. ordinarily the tank would be full of water to receive this heat and the water would get pleasantly hot. . instead the air in the tank receives all the heat. air expands when it gets hot , quite dramatically under the ideal gas law PressureVolume= n ,number of mols x R, ideal gas constant, x Temperature. in a tank, empty of water and full of air, pressure in the tank goes up dramatically, proportional to the rise in its temperature from ambient-- say 70 degrees to 200 , the hose temp. that increase of pressure inside the tank will bust seams and mess up gaskets for sure. same result: if you turn on shore power and have a tank that has leaked out most of its h 2 0....

 

[Johnb]

Temperature. in a tank, empty of water and full of air, pressure in the tank goes up dramatically, proportional to the rise in its temperature from ambient-- say 70 degrees to 200 , ...

Doesn't it go from 529.67 Rankine to 659.67 Rankine which is a lot less from a pressure increase point if view. If I am wrong forgive me because I am just an electrical engineer.

 

[Davidasailor26]

that increase of pressure inside the tank will bust seams and mess up gaskets for sure. same result: if you turn on shore power and have a tank that has leaked out most of its h 2 0....

The tank should have a pressure relief valve to let out the excess air pressure before any damage to the tank. The problem with turning on the electricity without water is that the element will burn itself out without anything to disperse the heat.