Identify this cylinder head please

[vrunner79]

This cylinder head came from my father´s shop
I do not remember which model & HP was
54475

[Mark Suter]

This is the port-side cylinder head from a Johnson model PO-15 motor (22.5 hp... not a racing model). The head assembly contains a compression release valve (the hole at the top of the picture is the port through which the compression is released and the boss above that hole is where the release valve stem sticks out so it can be depressed with a lever. The two tapped holes on either side of the spark plug hole are for mounting a cast-aluminium spark plug over. Hope that helps.

[vrunner79]

Thank you very much..!