OK, here's my perspective. If we agree that there's a difference between right and left turn due to the engine direction of rotation, then that would be due to a reactive force from the engine's rotating mass, and through a reactive force from the resistance against the propeller. We call this torque effect, which is partially correct. RC boat engines came second in the ranks of model engine use, and as they were converted aero engines suddenly we had model boats with engines that defied the conventional direction of rotating, through being mounted backwards. So full size boats have propellers that rotate clockwise when you are facing forward, that is a 'Right Hand' propeller, so by definition, and against popular thought, the model boat engines are running left handed propellers (you'll find that the modelling fraternity actually call these right hand, go figure. It's because 'right hand' is associated with 'normal'). As a consequence, to maximise turning ability full size hydroplanes are fighting against a force that is trying to rotate the boat anti-clockwise when looking forward, so to use that they make left turns around the course. Model boats, as the engines are actually going backwards against the convention of full size boats, they make right turns on a course. With our aero engines facing the 'correct' way, the opposite applies. As such the most effective turns are to the left, so the turn fin should be on the left, or port, side with its function being to hook the inside of the turn.
This issue has bugged me for years, and it's one of the primary reasons for my building an in-line twin as it removes the difference, but if you check around you'll find that airboat hydros are mostly rigged for left hand turns, it'll only be the other way with a pusher engine.
I'm not sure where your aeroplane analogy sits to be honest, aeroplanes have a tendency to roll left for the same reasons as an airboat, reacting against the direction of rotation, as such a plane will flick into a roll left easily and with a bit of elevator your turn is there with some rudder to keep the nose up, going right needs more aileron. Rudder turns in a plane will be flatter right than left. But I'm not sure what the 'easy' bit means, it can be 'easier' to control a right turn because it reacts less, which is different to the plane's ease of getting into a maneuver.
Current evidence. Every SI3 hydroplane turns left on speed runs, every SI3 with a turn fin has them on the port side. My narrow built 'Miss FivePoint' has been setup so that I can turn the boat at full speed in either direction without the boat flipping, this was done by trial and error, the resulting turning circle to the right is three times the radius of the left turn.
It's interesting that you feel that right handedness means that right turns sit well with you. If I can use a tennis analogy to me it feels that right turns are backhand, and left right are forehand. I think there's a reason for that. I recall when I was younger that when I thought about my boats they'd be going right to left in front of me, a forehand pass, now I'm older I've become so conscious of keeping a distant boat in order that I picture them far away going in the same right to left direction, but now it's the other side of the course!