O.K. I replaced my impeller and am now having a hard time getting my lower unit (mercruiser) on and working right. I can get it on and I'm making sure it is in forward gear by rotating the shift shaft and ensuring the prop won't turn clock wise and the throttle lever is forward. But when I get it together it won't shift into reverse (handle won't go back)and the prop freely spins when throttle is in forward. By the way it's 102 degrees here today. Thanks. 