Originally Posted by Bill Krejca
I wasn't thinking motor submersion, maybe a cooling water hose broke loose, or motor perhaps run with cowl off while being adjusted?, or etc. Thanks again for the information, I have a bought new 2000 F115, runs great.
That's an interesting hypothesis, but I had the cowling off at the dock while I was trying to diagnose the issue and didn't see any evidence of water anywhere near the plug. It would have to be a pretty small leak to the extent that it dried during the ride back.
One positive note that can be said for all of this is that most of the damage was localized to the female side of the plug (bottom). Yamaha makes a 4' extension that sells for $50. I'll probably buy one and splice that in with heat shrink and mastic tape versus replacing the entire control wire since there is a lot of lead wire to work with. If the male side of the plug had been damaged (top brain box) a replacement harness is a whopping $500 and would take hours to replace. I'm fairly certain mine is clean enough to salvage. I just have to carefully remove the remnants of the rusted sleeve from the 12V pin.
I'm not in any way trying to knock Yamaha motors. Aside from this little debacle this has been a fabulous engine. It's getting pretty old and these things can be expected to some degree. I simply wish I had known about it because I'm sure cleaning it out periodically and using a bit of dielectric grease would have saved me this headache. It's not something I would have thought to check.