i recently purchased a 1964 mercury 650. i noticed that the motor is stuck in gear.(prop and shaft spin ccw together and click when prop is spun cw). I took the lower unit apart to replace the water pump and figured the problem would be obvious, but it is not!even with the lower unit off i can not manually get it into neutral. should the main splined shaft slide out to change the impeller? it is solid at this point. hope someone can help!!!!!!! don't want to do anything else til this is resolved.