Reverse
A couple of things are happening when you put the boat in reverse when still moving forward. As you mentioned the exhaust causes cavitation when in reverse. When going forward, the blades are not travelling through the exhaust and is therefore not a problem. The other factor is the blade itself. When you put it in reverse, especially at high forward speed, the blades are hitting the water broadside. A finer pitch prop will help this, but how much is questionable. If you are getting the speed you want going forward with a finer pitch prop, then it is worthwhile. If not, it gets very questionable. What I have tried, and it is very subjective, is to ease the throttle up so that as the boat slows down the blades are at more of an angle and are taking slices out of the water rather than hitting the water broadside. I believe that the reverse is totally ineffective if you are still moving through the water at a high speed with the engine at full throttle in reverse. What slowing you are getting is due to the drag of the boat itself. I believe that it is possible that you actually get more slowing when moving at max speed by just retarding the throttle rather than putting it in reverse. That all sounds sufficiently confusing, but try to visulize what is happening as the blades move through the water.
