Center the steering wheel and check the nozzles. If they are off, there is your issue. You have limited travel from about 8 o'clock to 4 o'clock. They nozzles should be centered at 12 o'clock. You can lay a straight edge across them to see if they are square. Not exactly the book definition of adjusting them, but it does work to identify alignment issues and when they are centered. This is just to see how much "wheel" you have left and right of center, since you mention you have more to the left.
However, you have two impellers, both turning the same direction, on either side of your keel beam. Stands to reason that your ability to turn would be better one direction than another, and I have read the following description of reasoning, written by Harry at Group K...it helps to understand the forces. Yamaha attempts to control much of the differences with different pitched impellers, and that does balance the thrust, but as for turning, you still have to counter the rotation of thrust. In a prop airplane, we have a number of forces acting on the airplane at any given time. In addition to gravity, the creation of lift also causes increased drag, and then there is slip stream, p-factor, and gyroscopic effect. We have a good many similar factors, although they are not aerodynamic, they are hydrodynamic forces. But we have forces similar to slip stream, gyroscopic effect, and p-factor, as well as drag. Without counter rotating engines, it will turn easier one way than the other, not to mention faster. And I think that is the nature of the beast.
