1993 Evinrude 150 wiring issues

Hello guys I'm new to this site and have been reading related topics and have found them very helpful. I bought a boat from an older guy the other day and the engine was not running, I checked compression and it was good so I bought the boat for a really good price, I took it home and saw that it was not getting fire so I started testing. I unplugged what I now no is the grounding plug into the top of the powerpack and got my friend to turn the key and he misunderstood thinking he should crank it and it fired right up and scared the hell outta me. But when I plug it back into the top of the powerpack and unplug the shift sensor it will still run but turning the key off will not turn the motor off, the only way to shut the motor off is to plug the shift sensor back up and the engine will die with the key on or off. This just seemed strange to me. Anyone have any ideas?