1977 Mercruiser 228 - Wiring Assistance

[Beachcraft 1]

I have a 1977 Beachcraft that has a Mercruiser 228 (305) that I replaced with a 350. The wiring from the harness is pre BIA color coding, so most diagrams don't match colors. I have three black wires from the harness plug in - 1) One that goes to alternator, 2) One to ground) and 3) One to either the slave solenoid/starter solenoid (see diagram). The problem I have is interperting the diagram, does the 3rd ground from harness connect to solenoid on same post as yellow (see diagram) or to a ground nearby (say to a bolt holding down solenoid).

I have a bypass wire from the start solenoid the the + side of the coil to run full voltage to the coil during starting. (Tan) The yellow ignition wire from panel (neutral start switch) connects to small post (see diagram). Then of course Red and Yellow from starter. Based on the diagram, can anyone tell me if the black connects to the small post with yellow from harness (two wires black and small yellow on same post) or to a bolt that holds slave solenoid on? Thanks.