I just bought two 2006 F-12's and finally got to take them out last Sunday. They started right up and ran perfect all day. I was totally impressed with the power and handling of the machine. Its break in time so I tried (and failed) to stay under 4000 rpm. I did stay under 6000 though and did not go over 40 mph. On the way back to the dock, the one I was on started vibrating alot when I tried to accelerate but would calm down while cruising. Any accelaration would cause a vibration. It also seemed to want to tip to the right after that. I checked the intake grate and it was not clogged. Upon closer inspection at home, I found a small piece of flat shell (oyster or something similar) jammed on the intake side of the impeller between one of the impeller blades and the housing. I pryed it out with a long screwdriver but have not had a chance to take it back out on the water to see if any permanent damage was done. Has anyone else had this happen and does anyone know the likelyhood that this may have bent the shaft or impeller? I'm new to the PWC world and would appreciate any advice on this.