Wiring question - starter

[Baja Boater]

I just bought a 1988 Baja 17 ft. Merc 3.0 4 cyl. Starter not working but fixed that. In the process of troubleshooting I see there is a wire from the solenoid on the starter lug that I am trying to determine what it does. The starter solenoid gets the start signal from a relay. That works. There is an extra wire on that terminal as well as a wire on the other terminal that is hot while the engine is cranking. So the question is . .. What other - - it seems - things are energized while the engine is cranking ? Hope that makes sense.
Thanks

 

[alldodge]

I think your talking about the 90 amp fuse. The pic below shows the wiring, but does not show the orange wire for the alternator on the fuse which it should

 

[Bt Doctur]

the small lug closest to the engine gets the wire from the slave relay or solenoid., Yellow/red. The other small lug purple/yellow is energized only during the cranking phase and usually goes to the + side of the coil if points are used or to the electric fuel pump pressure switch NC post