M_Boats: OUTBOARD FUEL

I presently have a 6 year old 4hp Yamaha on my 17. Yesterday I was reading the manual and it warned "NOT TO USE FUEL WITH MORE THAN 8% ETHANOL". As you all know, normal auto fuel contains at least 10% ethanol. While I have not experienced problems, I am wondering if I am damaging my engine. I don't know of anyplace to get 100% petro fuel. Any experience, advice or opinions? Arnold Sharpe, M-17 #265 "LITTLE BREEZE"