The screw goes through the casting, bangs up against a brass plate #69, which squeezes a rubber spacer #68 against the liner #67. The liner is slitted which allows it to squeeze down on the pivot shaft to increase the friction.
You didn’t say, is the steering too tight or too loose? If too tight, backing off on the screw probably won’t help because the problem likely is corrosion. The cure for that is take it apart and dig the corrosion out. A common problem here in the land of salt and sea. Done lots of them.
