Mercruiser Fresh Water Cooled Cabin Heater

rossjo · Post by **rossjo** » Fri Nov 06, 2009 12:14 pm

I want to hook up an in-cabin heater to the fresh water cooling system on a 7.4L Mercruiser (on my other boat).

I have the stock, Mercruiser FWC system, and am not sure how it should be connected. I assume I use a "Y" valve like olde cars used to channel water to the heater core when needed, or straight through to the heat exchanger when not needed.

Any help or pix would be much appreciated.

Danny Bailey · Post by **Danny Bailey** » Fri Nov 06, 2009 8:27 pm

See if you have a plug somewhere in your circulating pump. This is where old cars picked up the pressure side of the heater water. The return from the heater went back into the intake manifold, upstream of the thermostat. If its not plumbed up right your engine will run cold.

alexander38 · Post by **alexander38** » Sat Nov 07, 2009 7:44 am

Here's an ideal I use aux heaters in my fedex ground trucks I get them from mill suppiy .com. You can get them with the fans and all the switches. And run the hoses just like you would for water heater set up and put in cut out valves to shut off the water.

rossjo · Post by **rossjo** » Sat Nov 07, 2009 9:05 am

I have the stainless heater core complete with fans already. I just need to know what the proper connection to the Mercruiser (same/similar to Crusader) FWC heat exchanger is ...

I thought I could add it to the existing FWC hoses, but found my manual, and alas, you are correct ...