I replaced the input shaft seal yesterday on a B3, and when I did the runup on it, If you are in neutral and throttle up the drive it will kick into gear and release in both forward and reverse, I don't know if it was having this problem before the leaking seal or not, the customer did not say, I disassembled it and checked the gear timing, and check the cable adj. it was OK, any Idea's

Replace shift the cable and reset the shift alignment with the proper Mercury shift alignment tools.