Re: 1971 100 hp Evinrude Shift solinoid wires.
Your motor is an electrically actuated hydraulically shifted gearcase that has a clutch dog that is spring loaded into forward gear as a safety feature in its day.
It takes hyraulic pressure and power to the green wire for the gearcase to shift into neutral. If it doesn't, then there may be wrong oil, water in the oil, broken oil pump or check valve, or problems with the shift solenoids either mechanically or electrically.
You will need to troubleshoot the system per the service manual. First make sure there is 12 volts on the green wire going to the gearcase when in neutral.