1988 50 Hp Mercury Outboard My Mercury Outboard Doesn't Seem To Go Into Reverse Gear?

My mercury outboard doesn't seem to go into reverse gear? - 1988 50 hp mercury outboard

1983 50 hp Mercury outboard with Teleflex Cable Suntrack pontoon boat in 1988. From the water and running motor controller, when I test it in the proposed changes in direction, according to the instructions. Conversely, if prop in both directions. I put the cable on the border and still wrong. I do not want to deal in water until it is known for. Engine must be running in order to invest thogh proposal not on the head when I take off headsets and the engine running. Follow seems to work well.