Sorry to revive this thread, but I just went through the process of removing the lower shift rod brass bushing from the lower unit of a 1990 Johnson 30 HP (J30RESS). I suspect that this issue would apply to most 15-35 HP J/E outboards with through-prop exhaust.
I was just replacing all lower unit seals and didn't want to dismantle the entire lower unit to do so - thus, I couldn't apply the method described by 'fdrgator.' What I did, kosher or not, was to remove the lower shift rod, stuff a bit of paper towel in the bushing so that it 'sealed' the hole (the paper towel bunched up behind the o-ring and plastic washer). I then tapped the brass hole with 5/16th-18 threads, screwed in some 5/16 threaded rod and pulled the bushing out. No brass shavings made it into the lower unit gears because of the wadding, which came out with the bushing. I re-used the bushing (with NEW o-rings) and it works fantastic and there is no excess play in the shift rod since the ID of the threaded bushing is essentially the same after tapping. I hope this helps.