cavitation?
If there's a problem in cavitation or aeratioin, it would most likely be cavitation if it affects the performance of the propulsion system. If the boat revs but you get no thrust, due to as you say, cavitation, that means it has to originate from somewhere between the suction, under the boat up to the impellor. Anything after that would not affect the performance of thrust. If you aerate the output of the thrust, so what if a few bubbles got in your jet stream, this shouldn't affect forward thrust. I would look at the clearance on your wearing ring and the impellor itself. If your impellor shows any bent blades or damage, you can replace it through sbtontheweb.com. They have all the parts you need to rebuild your pump for about $200, impellor for $25 with a trade in (core). In this situation for me, when my impellor wearing ring folded in, the boat reved up and there was a little water that came out the back, but it seemed aereated and there was no thrust. You've stated that you've already checked all that, but there really isn't much more on the propulsion system it could be..........I'd also make sure your splines to the motor's flywheel and the splines leading into the pump are o.k....One more note, now that I think about it. Look at your reverser. Out of the water, put the drive linkage in forward, go to the back of the boat and look to see that the nozzle is fully open. If the reverser is out of adjustment and hanging in the path of your forward thrust, this may have the ability to lift the boat out of the water just enough to cause cavitation........that's really going out on a limb, but it seems logical to me that this could happen with the type of power these Rotax engines have. I hope you find your problem!..........hold on!...I just happened upon a section in my shop manual explaining the problem in cavitation where the impellor can actually suck in air from within the hull, where the shaft, grate lever, etc....pass through the hull of the boat. Check for lose cable fittings and seals at shaft. There is a carbon ring on mine that is essential in sealing my shaft where it passes through the hull.......
