Need info on FWC conversion for GM 350/Merc 5.7 Alpha 1
 

I am putting in a new GM 350 engine and looking for info and diagrams to convert to fresh water cooling. My old system is a Merc 5.7 Alpha 1 with a thermostat housing that has 6 hose connections and cannot be used for FWC.

Have checked Mercruiser microfiche web site but they are not clear on the housings or flow paths. I have old Merc Type 1 manuals which are very clear on this but the new ones are vague. Does anyone have diagrams on this or know which type of thermostat housing to use?

Doug

Your Alpha 1 is set up with a raw water pump in the drive and as such is not the best candidate for fresh water cooling due to the fact that it does not flow a sufficient amount of water to work with the heat exchanger. That doesn't mean that it can't be done. I've heard that it will work OK if only cooling the block in this fashion.

The best thing is to convert to a engine driven raw water pump like the ones used in Bravo 1 applications. It will supply all the water you could need.

My '83 Alpha 1 setup has four connections, one each to the manifolds (the risers are fed internally from the manifolds), one incoming from the raw water pump, and one outlet going to the input of the circulation pump. As far as I know the thermostat housing is original. I don't know if this helps you at all but at least it's a start.

Doug, you will need a sea water pump kit and the heat exchanger kit. Plan on spending about $1000 for new stuff, but in my opinion it is money well spent.