Reply To: 1969 4hp Folding Johnson Outboard not circulating

[Don]

You just have to be mindful of that “lyfanite” coating that is found in many of the cooling passages back then…You don’t want to loosen all that up and have it floating around in there… That cooling exit passage “elbow” is the tricky part on these engines. You can only get at one side of the elbow by passing a long drill bit/punch up the vertical passage on the right side of the powerhead… If the lyfanite coating isn’t present in that passage, then by all means try something like CLR (the safe for aluminum variety). Again, those plugs in the elbow can be removed, but be sure to procure new ones prior to ruining the old ones while removing them..