The rest of my parts just came in and I'm ready to get my motor back together and running, but I have one question. The water pump kit included "o-ring, drive shaft". Where does this o-ring go, inside the pump, on the upper end of the shaft? When I pulled the lower unit, the old o-ring fell out. My guess is that it was on the top of the drive shaft right below the splines. There's a small groove there that the new o-ring fits into perfectly. I just don't see what purpose it serves being in that position.