the mercury switch is just a glob of floating mercury in a bottle which closes 2 contacts to let the ground pass to operate the solenoid if... the engine is not tilted up or in gear on diff. engines mdl.
just short the 2 wires (if 2 wires) as a qwick test or measure the ground ohms each side of the switch wires with the engine frame ground ....should be the same value ) 0 ohms .
if single wire switch make certain the switch body contact to engine frame is clean !!
to service your oldy. this book for $20 has all you need !!
Johnson Outboard Motor Service and Repair Manual # 302231 Tenth Edition covers all Models 1922-1964 .pdf download
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