I have alpha one mercruiser and it will not shift in reverse and forward. I can get one or the other but not both. Tried every way possible to adjust cable with no luck. I can shift it into gear and get out of boat and turn shift lever on outdrive with screwdriver and I just have to move it a tiny bit to get it to take gear but can not get it to engauge without screwdriver. Any ideas would be greatly appreciated.