Per your picture, see the milled slot right under where your arrow is located? Consider this: Any oil that manages to seep through a less-than-perfect upper crankshaft seal would run down that slot and be drawn off to the intake manifold, along with any oil that manages to escape around the outer shell of the bearing. The same scheme was used on bushed engines that had a slinger only and no seal. Hey, good or bad, agree or disagree, it was the OMC way at the time.
BTW, my estimate is that most of the black crudded up armature plates back in those days were from vibtation-liquified over-greasing of the armature plate support rings. Of course this is now and the seals have had a lot more time to start excessivly leaking.
