I’ve got the owners manual/parts list for that little gem. Unfortunately, after 45 years or so, the drawings are faded some, so the shape of that cam is hard to discern. The part # is 157-477, referred to as a cam – Neutral Clutch.
My only recollection of that part is that it has an offset straight edge, so that when you move the handle, it passes above (or below) the tab on the clutch. I’m pretty sure the Eska/Gamefishers of that era also used that setup..
If you want the manual, send me a PM. Just looking for a buck plus stamps..