The Minneapolis Star Tribune, in the FixIt column for today (linked above for the couple of days it will be active) says:
After I finished laughing, I wondered if it was possible for them to have been correct. Since steering on the starboard side has been around since ... well, since it was the steerboard side, long before there were propellers, it seems unlikely.
Q Why are boat steering wheels and controls on the right side rather than the left side?
A Boat propellers turn clockwise. Hulls used to be designed in such a way that when there was torque on the prop, the right side of the boat would rise up. The wheel was put on the right so the weight of the fishermen would counteract that.
This is not a problem with modern hulls, but the design stuck. Racing boats usually have the wheel on the left, like cars.
That it's because of the starboard to starboard passing rule is continuing the tradition, not establishing why the tradition exists.