I had to replace my stock control box on my 1977 Renken tri-hull. The boat has a Mercruiser 120 (GM inline 4). I replaced the box with a Morse MN series box. I purchased a 600A cable that is 13 feet long to use as the shift cable and a 15 footer for the throttle. I hooked up the cables to the control box. When I went to hook the other end to the plate it would not adjust big enough. I put the drive in forward by hand with my son turning the prop. It locked and I was able to adjust the cable so that it mated up. It shifts forward and neutral fine but I have no reverse. I have searched high and low for the answer. I have a manual coming but it will not be here until the 10th. How do I adjust the system? I am confused with the other posts and instructions. Do I have to adjust the shift cable that goes out of the transom to the drive?