25 hp yamaha grounding wire fire
 

So I needed to remove my motor from the jack plate.... I disconnected the wiring from the battery; positive wire first and then the grounding wire that runs into the lower unit caught on fire and burned the wire in half. It's a 2014 model. How important is this wire? Engine still starts and runs. Just wondering what I've done!!!!

Does the tilt and trim still work

I think its a ground wire that acts like a fuse. Definitely replace it.

If it's a small black wire coating then yes replace it it acts as a ground when that normally burns up that means there was some type of current grounding out either the motor or boat