I will venture a guess on this one. It has to do with the effects of rotational torque on the boat when the driver gives the engine full throttle. If the helm is on the right side of the boat and the driver is the only one in the boat, hence no other weight from other people, when sudden full power is applied the boat will torque or twist counter clockwise. This would have a tendency to lift the right side of the boat which is where the driver is sitting, therefore keeping the boat more balanced under full throttle. If the boat was running a standard/left hand rotation engine and left hand prop it would twist/rotate clockwise, throw the boat out of balance because of the drivers weight on the starboard side. The boat would have a great tendency to list starboard under load. Does this make sense? Maybe only in the crazy world I live in.
Car engines turn left hand, twisting the body to the right and lift the drivers side up. Watch drag cars twist and you can really see it. But what about cars with the drivers seat on the right? Oh well, I'm really confused now. LOL
BTW, absolutely a great web site Paul. I've been reading for months and really enjoy it. Thank you!