fried wires

I have a 1987 50elh Yamaha which is a 50hp 2 stroke. I have only had it running once before I put it up for the winter, and it seemed to run fine. I did notice later that every ground wire on the engine had the insulation cooked off. I sure it has been like that for quite a while. I repaired/replaced the wires and haven't ran it since then, I took the motor off to replace the transom, anyway any ideas out there as to what could have caused this? I won't have it running now.until spring but I'm curious as to what.the problem would be if any. Thanks and Merry Christmas

Is the engine an electric start? If so then the main ground wire was loose at one time and the current found its way to ground through the smaller wires. There was enough current to overheat the wires.
Always make sure to use a tool to tighten battery cables to a battery. I never use wing nuts on a battery for this reason. Always use hex nuts and tighten with a wrench.

Thanks, Pappy. Every day I learn something on this site. This subject is my "learning" for today. regards, R

Don't feel bad. I never thought about that either. There go the wing nuts.

That answer makes sense, that Pappy guy knows his stuff
Tim