Re: 1957 Johnson Rd 19 wires
The mercury switch grounds the body of the vacuum cut-out switch, but only at slow throttle settings. That enables the cut-out switch to control run-away. The reason for enabling it only at slow settings is because if it were to be enabled at high speeds, it may cause an erratic miss, especially at cruise throttle settings.
On electric start models, the switch serves dual functions. It allows the electric starter to function only at slow throttle settings.
Good luck reconnecting that wire. The post on the switch is stainless steel and is not solderable. The wire was originally welded on.
