Merc model 9.8 s/n 6404396 1983??? won't lock down in reverse and won't shift into reverse sometimes. When it does shift and the motor is turned to the left when facing the motor from back it will lock down. Is the upper screw in the l/u used when you change oil a small phillp head and not a larger sloted head. Also is there a sight on the web of diagrams of parts for mercury motors 1975 or so and up. Thanks for time and advice.
