I have a Ser#3577714, 1971 Mercury 50 H.P. outboard motor. I am trying to find out how to set the cables at the engine so that it well operate correctly. Right now it goes into forward but not in reverse. I have heared that they are calberated by inches but I cannot find any thing in a manual on this type of motor! Can you help? I am lost!<br />Also the spark plug wires were wrong too when I bought it.