Thought I would share this. This happened to me about half way through our 350 miles of rain on the way to Bogalusa. The next day I went through all the connections and found them to be still clean, dry of water and greased with dielectric grease just as I had done a year ago.
Symptom: Any audio source from speakers is severely distorted. The distortion is so bad you can not understand anything. This initially occurs at a volume setting of about 18 or above which is my normal cruzin' level. If the level is kept around 10 or so, it sounds ok for a while but eventually becomes distorted. All the while the head set audio is clear. The dealer has ordered a replacement audio amp unit (warranty) after confirming with Yamaha that is is a known symptom. Just as a side note, the retail cost for the replacement is $1400.