Re: Looking to find out what this wire is 1986 merc 175hp !!!
I answered a similar thread yesterday. Red on Merc is 12v hot wired to the battery....may contain a fuse. Purple is 12v hot "switched" by the off/on switch on the control box.
Looks like the power line for your trim and since you can change your trim with the ignition off the wire is red and connects to the battery (eventually). Follow the large red wire (from the wiring harness) to one terminal of the starting solenoid....other terminal connects to the starter.
Merc uses this terminal as a 12v distribution point. If you can't find the other end with the other half of the fuse holder (20A 3AG fuse) go to an auto parts store, get one and hook to the terminal using a suitable crimp lug. When finished, ensure the connection is goot-en-tite.
Mark
Mark