odd wiring harness?

[Soundslikefun]

I have what I have found to be a 1964 Mercury 65 hp. The wiring harness inside the motor does not match up with the wiring harness outside the motor. The 4 gauge positive red battery feed inside the motor is tied into the green 14 gauge outside the motor. The 4 gauge negative black battery feed inside the motor is tied to the 14 gauge black wire outside. Is this typical? Outside the motor I run accessories using red as ground and green as 12+?

My wiring had dry-rot so I pulled out both harnesses and just ran all wires directly to the motor. Saved $400 in harnesses. Any red flags you see in this approach? I have them taped up, tucked in some split plastic wire casing which is also taped.