# Mercruiser 5.0 / water heater install??



## Snagged Line (Sep 30, 2007)

I installed a water heater in the boat so that Donna will useALL of the onboard fresh water at once, rather than conserving it to last all weekend..................


The water heater has a internal heat exchanger that will allow hot water from the raw water cooling system for the Mercruiser 5.0 to flow through the heater and heat the water whenever the motor is running....................

I have found the plug in the GM water circulating pump on the front of the motor where I need to install hose fitting for the hot water supply to the heat exchanger, But I am unsure where to route the water line leaving the heat exchanger once it has passed through the water heater.............( it is much like the old '50s and '60s automobile heaters that the heater hose comes off the water pump heater hose connection and ties back into the block <span style="text-decoration: underline;">somewhere once it has passed through the heater core )

Does anyone else have the same setup that can give it a look and tell me where to route the return line???? Thanks in advance...........................Dennis


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## RPM (Mar 18, 2010)

if memory serves the fitting on the water pump is the return since the circ pump is pumping water through the block, up into the heads and out the thermostat housing eventually out to the manifolds and risers. the inlet line to the heater would need to go just before the thermostat. look at the housing below where the hoses come off and there should be a water temp unit on one side and possibly a water warning switch on the other. if you dont have a pipe plug there to install a nipple you might drill and tap the housing or ive also seen them plumbed in to a plug in the water runner leading from the head to the tstat housing at the front of the intake manifold. im not to keen on this placement as the runner on one side is doing double duty but it works. worse case a second plate/spacer in between the tstat housing with a tapped hole would suffice. be sure to use the tstat housing gaskets with the bronze rivets in it to ensure good electrical bonding.

ce


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## Snagged Line (Sep 30, 2007)

Thanks for the response, I belive it is just as you described it.............I'm gonna try to find one to look at so I can take notes on how everything is routed and try to duplicate it. Thanks again, Dennis


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