The mercury switch is clearly there in the picture. But the wire appears to be burnt off from it. The wire is supposed to be welded to the little pin sticking out of the mercury switch. Welded because the pin is stainless steel and unsolderable. It is very common to see the wire burnt off like that. It happens almost instantly from improper attempts at troubleshooting or jump starting.
Bottom line is it can no longer function as it is now. In other words, its purpose is to prevent electric starter operation at high throttle settings, and if the starter is working, the system has been defeated somehow.
BTW, excellent picture.
