Ha! I figured as much. That solenoid looks straight off a truck lol, and most of the Yamaha's I've dealt with had the 30amp starter relay instead. I really appreciate the reply. I'm guessing on the relay box, it may be for the towing/trailer kit that they added to the bike (best guess), and glad you commented on it. If able, I'll just pull it/wires completely (I'll look this afternoon and see if I can follow the leads all the way back to where the hitch was.
Thanks for the reply, truly. I priced/ordered the starter relay (guessed at it, before your reply) for 8.87 off amazon, and battery for 60$. Hopefully this weekend I can get in there and replace all those suspect battery cables/terminals and the solenoid/starter relay.