The silver piece you refer to in post #14 should be the choke lever (points downward). Using your finger, you should be able to fully close the choke plate with the lever (pulling forward). Assuming the linkage works OK, I think the choke lever travel might be limited by the way you have the plastic knob installed. The plastic stem is slotted, if like my smaller motors, and slides over that choke lever at the bellcrank.
On my smaller motors, the plastic knob can indeed be installed upside down (see racerone's post (#16)). The angled slot in the stem properly fits over the choke lever in such a way that the lever gets full travel. If it's upside down, the choke lever won't have full travel and the choke plate will not fully close -- lever movement will feel like it's blocked.
If your choke knob attaches differently, a picture of the knob and stem or additional description would help on this end.
[Edit. I'm assuming the plate rotates counter clockwise to close on yours (lever pointing down). I think it might be the opposite direction on my 9.9s.]