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Old 25-05-2020, 10:13   #1
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Boat: Niagara 35
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Westerbeke W40 water heater install

I have researched and researched and researched and still canít find a solution to my problem. So today, after 2 years of engine overheating issues and trying every possible solution, Iím going to ask for help.

I installed a 6gal water heater on my Niagara 35 a couple of years back. I was going to install the heater hoses in parallel, as most people do, until I found a service bulletin from Westerbeke stating that a water heater should be installed in series in the coolant system. As per the bulletin, the coolant hose coming off the exhaust manifold and going to the heat exchanger should be interrupted, go to the water heater with a bypass nipple to help with flow if the water heater coil is too small and return back to the heat exchanger. And after 2 years of trying to make this setup work by eliminating every other source of possible overheating issues, Iíve come to the conclusion that I need to have the water heater installed in parallel.

Iíve read every thread I can find about this topic but canít find an answer that works for my specific situation. The engine is a fresh water cooled Westerbeke W40 with a V-drive. So my engine is ďbackwardsĒ. There is a plug next to the thermostat which I assume is meant to be used for a water heater but unfortunately it is seized. Iím still attempting to get it out but havenít had any success yet. There is a coolant temp switch to activate an alarm at the front of the block which I no longer need so I thought I could tap off of that as a feed or return to the WH. I can also tee off of the coolant temp sender. There is also a plug in the top of the heat exchanger which I thought could be a potential return point but this would be bypassing the thermostat when itís closed so itís probably not a good idea.
So with all that said, can anyone give me a good solution?
The water heater is installed about 8 feet forward of the engine and the coil is below the highest point in the system. The hoses have to run under the cabin sole and then back up to the water heater.

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Dylancs is offline   Reply With Quote
Old 25-05-2020, 13:25   #2
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Re: Westerbeke W40 water heater install

The best way to remove a difficult plug, nut, or bolt is with an impact wrench. Many rental places have electric ones. Sometimes auto parts stores loan them. Cheap tool companies sell them for about $50+. An impact wrench usually works when a wrench or socket just twists the head off or destroys itself.
Almost all heaters bypass the thermostat. If you're having heating problems it shouldn't matter. The issue of bypassing the thermostat can be solved by a 12v water solenoid valve in the line, a heat sensor or timed relay that opens the valve when the engine is warm or so many minutes after the engine is started. The valve could also be controlled by a relay that operates when the heater blower is on or the water heater is below temp.

Another way of taking heat from the cooling water is a tee installed on both sides of the heat exchanger. You need at least 1 valve to regulate the flow.

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Old 25-05-2020, 14:25   #3
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Re: Westerbeke W40 water heater install

Thanks for those suggestions. Iím still working on the plug. I have an impact gun but just need a new length of air hose. Iíve been spraying penetrating oil on it for about a week now but it sounds like I may not need to take it out.

So if Iím understanding correctly, I could remove the coolant temp switch and have that as the feed for the WH and then return it to the port in the heat exchanger. Maybe Iím overthinking this, but would there still be suction on the return line to the heat exchanger when the thermostat is closed? Would it be better to have the feed line be from the plug that is currently seized (if I can get it out) and return to the coolant temp switch port? In the first scenario, without a timed or temp sensed solenoid, the engine would take a little longer to heat up as some of the coolant is bypassing the thermostat while the engine is warming up. I have also read suggestions of putting a restrictor in the feed line, say 1/4-3/8Ē, to only allow a limited amount of coolant to go to the WH. My plan was to put a shutoff valve in the feed hose so I could experiment with the system once itís installed. My understanding is that I wouldnít need a bleed valve in the system if the WH coil is below the top level of the coolant system, (which it is) the coolant fill cap in my case.

Thanks for any and all help. After 2 years of only being able to use 60% power before the engine starts to overheat, Iím desperate to get this right while also having a functioning water heater.
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Old 25-05-2020, 16:10   #4
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Re: Westerbeke W40 water heater install

I think Iíve had a eureka moment after thinking this through a little more. Someone please correct me if my thinking is wrong.

I think my concern about bypassing the thermostat to the heat exchanger when the thermostat is closed wonít be an issue. If I feed the water heater from the overtemp alarm switch port which is in the thermostat-closed circuit and return to the heat exchanger, there wonít be suction on the return line when the thermostat is closed. Therefore -again, someone please correct me if Iím wrong- this would then mean that coolant wouldnít flow to the water heater until the thermostat opens and suction is created at the heat exchanger.
Make any sense?

As a side note, the reason I no longer need the over temp alarm switch is because I installed a NMEA2000 analog to digital interface which converts the analog signals from the engine senders to a digital readout. So I can watch my engine slowly start to overheat in large, easy to read numbers. Iíve also calibrated an over temp alarm through my MFD so the analog sender is no longer necessary.
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