Cavitation problem 93 xp 650

[944v8]

HI: newbie here; I just replaced the shaft bearings and seals. When I looked at the impeller it a had a few nicks but nothing strange or large. The rubber ring did have 1 (one) pencil lead width grove 3/4 way around the ring. THe ring and impeller where very tight.Difficult to turn with out soapy water for lubrication. Just seemed nice and snug.Put it all back together and ran fine for 1 day. Now full throttle coming out of the hole the RPM goes from 4k right to 7k and no thrust.Just cavitation like you would get from an outboard prop that was pushing air instead of water. IF I go slow it seems to be fine.If i then go full throttle or get in 8-10" chop I get reduced thrust.The grate is clear. IF the ring was real tight I can't understand the cavitation. I did suck in some lilly pads, before this seemed to be a problem. Could stuff like that bend the impeller? I'm at a total loss. Every thing seemed fine when it went back together.If I pulled the nozzle assembly what would I look for ?
Thanks for any suggestions.

 

[944v8]

Thanks Steve:As you said the clearance seems to be .04 max between the impeller blades and the wear ring (according to the manual) . BTW I also replaced the motor mounts. But the shaft has a bearing surface in the hull which I would think would line everything up. Is there a special way to insure the center line of the shaft is true. Does one loosen all motor mount bolts and then sort of let the engine settle in the correct place using the hull bearing as a ref point.Would this effect the true running of the impeller. I realize this is probably a dumb question but I'm at a loss here at what exactly caused this problem. Obviously I can chk the clearance. If it it now worn out I must have done something wrong with the motor mount replacement. All shims were put back exactly as they were taken out.I also suspect that impeller balance could be an issue if the chips are bigger than what I think is "small"
Thanks