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the white wire is the ground side of the starter relay which must go to a ground referrence (mercury switch) typically if the engine is tilted UP the mercury contacts will be open and ground reference is lost and starting will be impossible.
the vacum (cut-out) switch where your mercury switch meets is itself normally NOT grounded leaving the mercury switch to do it’s job by itself.
the vacum switch is there to kill 50% of the ignition has described in the manual and since you would not be turning the key to START during that event the 2 wires would not interfeer between themselves.
they work together.. the Mercury switch PREVENTS starting during tilt up The vacum switch kills 50% of the ignition by grounding the lower plug (see manual) see diagram from MarineTech site
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I don’t know what you have there but
the solenoid has 2 small control posts & 2 big posts allowing battery high current to reach the starter while…. the inner small coil gets battery from the key START and the other side is grounded via whatever safety device hooks up to it to prevent false starts.
as far as I know NO VOLTAGE should pass between a large post to a small post. the big posts being simple relay in and out lugs…
isolated from the rest of the world
the small posts control the solenoid inner electromagnet to close the contacts when starting. the marine tech drawing is what you should use imho.
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I am going to try to cut through some of the confusion here——from memory, lacking an official 1957 parts book or wiring diagram.
1. 1957 was kind of an oddball.
2. There are two kinds of starter solenoids, looking exactly alike. But they are different inside. A car (Ford) type sends 12V to the coil, bypassing the ignition resistor while cranking. That is not the one you want because that 12V cranking whallop will burn the wire off the mercury switch. The type used on OMC outboards has the same two small terminals, but they are connected to the two ends of the pull-in coil inside. When you operate the key or button to start, 12V is sent to one of the small terminals, goes through the pull-in coil, and out the other small terminal, finally to ground through the closed mercury switch. The coil resistance provides a voltage drop so the mercury switch does not “see” a full 12V.The mercury switch is either open or closed, according to throttle position. If closed, the solenoid wire is grounded, and the motor will crank. If open, the solenoid wire is not grounded, and the motor will not crank. Simple as that. Note: because the mercury switch is mounted on a moving part the ground is not reliable. That is why the mercury switch body is grounded by a separate wire.
All this was changed in 1958, and the one diagram posted above is not correct for 1957.
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