my 2000 Xl800 was experiencing cavitation when I started out and the engine would rev up to 7000 rpm and not go anywhere. I replaced the impeller with a remanufactured one from SBT and also bought a new wear ring and housing. the wear ring is plastic. after installing it I water tested it. the very first time I had only a slight rev up and it took off like it should. after stopping and starting several times it got so bad I can't do 10mph and won't get up on plane. it just revs out. what else could be wrong?