4L60E Internal + External Wiring Harness | Drivetrain Resource The external wiring harness for a 4L60E will need to be spliced into the main wiring harness. It’s not that difficult to do, just make sure that you solder it in and cover it with heat shrink. GM 4L60E Transmission External Wire Harness 1993 and Up . mercury outboard external wiring harness | eBay Mercury Outboard External Wiring Harness Motor to Panel Push to Choke Ignition See more like this. MERCURY MARINER OUTBOARD EXTERNAL wiring harness cable 9 WIRES 7FT LONG APPROX. Pre-Owned. $61. From Australia. or Best Offer +$45 shipping. Watch. MERCURY OUTBOARD SUPPORT, EXTERNAL WIRING HARNESS 37692 . Pre-Owned.