I installed a new impeller and now have trouble lining up reinstall correctly. Should the gear shift be in forward, reverse or neutral? I can spin the prop either direction with some effort and watch the flywheel spin in any gear. The shift shaft has a small hole near the top. Can this be turned to line up neutral in the lower unit? Do I need a special tool or just anything that will fit in that small hole? Does it pop up and down, there is a small boot at the other end.