Hole in rear of head on 3.7l 1988 Mercury Marine motor

[Islander221v]

Hope some knows. There is a round hole in the head at the end beside the rear lifting hook. It appears to be about 9/16" around. At the front end of head there is the same size whole but it is plugged, does anyone know what these are for, the rear whole has air coming out of it.

 

[Eric 3.7LX Alpha 1]

I believe that's a core plug hole/ freeze plug.

A quick search says:
Ford part# is DOZZ-6026-B
or 17mm Napa P/N 219-2188
or Clevite EPC 224A

 

[Islander221v]

I believe that's a core plug hole/ freeze plug.

A quick search says:
Ford part# is DOZZ-6026-B
or 17mm Napa P/N 219-2188
or Clevite EPC 224A

Thanks for the quick reply, $8 frost plug at NAPA,