Wires go to the solenoid, governor, and rail switch. A lot of mechanics used to bypass the rail switch when they went south because they couldn't get a new part. The rail switch was discontinued in 1951 for the Mercury models so they are near unobtanium now. The old ones can be repaired if a person is careful taking it appart.
You may need to remove your solenoid and clean the internal points. This would give you an oportunity to test its function. The rail switch turns the system off when it's locked out. The governor turns the system on when it reaches a certain speed. For safety sake it's a good idea to get all the system parts functioning correctly. The 49 through early 51 Mercs may not keep the solenoid from engaging when it's locked out if the rail switch is not there to turn the system off. It doesn't have as positive a pawl locking device as the later Merc overdrives do when shifted to lock out.
Kerby
