I think you are right about the two opposing O rings. Before I even got down to your description I was thinking that. They probably will burn up quickly and possibly cause it to bind. Mine of course didn't have any O rings.
So are you saying they are referring to the moving outer cover as the slinger? I would imagine you could use a thin feeler gauge to set the spacing between it and the bearing retainer. On mine I can't recall how it was set. I think for testing I just put it on and let go. (but testing didn't get very far.)
Paul - that's my theory (the slinger is the moving outer part). When I see the various motors being offered (new and used) that part seems to be the variable. I've psoted this question on a number of different forums and haven't got any responses other than yours so far. I'm kind of surprised about the apparent lack of information on this topic.
Rick, I wish I could tell you what I did... But I never got that far. It was still blowing fuses. The board was OK ...but now I've shipped the motor off to the same place to see if it's shot. When I was testing I was doing so without the motor mounted to the gear box.