Need help to remove a rock or pebble, the impeller is jammed, so it won't start because the impeller wont turn. I can see that it is trying to turn but there is a rock lodged in there somewhere. I've taken the grate off and looked at the drive shaft but the seems to be no were to put a wrench to try and reverse it so the rock will become loose, which was my only idea for how to try and fix it. I thought of puting a pipe wrench on it to turn it backwards but I don't want to do any damage to the shaft that may affect the preformance, since the pipe wrench will likely chew up the impeller shaft when it bits into the shaft. Any help would be appreciated. Thanks in advance. My machine is a 1997 Polaris SLT 780.