Hello Naidni and :welcome: to iboats.
As the thread you posted to was more than 18 months old, I've separated it off and created a thread of your own. We can let the original thread stay in the archives
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This is the thread you were referring to ->
http://forums.iboats.com/forum/engin...heat-exchanger
As Merc have not used the 250cu in block since 1981 it would be unwise to attempt to put closed cooling on it. The scale currently in the block would be flaking off and cause major blockages in any HE you fitted.
Simple answer.. Can it be done, yes. Should it be done, no...
HTH,
Chris......