This question gets asked on boating sites ALOT! And my answer stays the same. What is the "value" of running that old gas in a high performance outboard? Ok so he had 15 gallons of 93. At todays prices at $2.50 a gallon that is $37.50. If he clogged his injectors/carbs only and didn't do any damage too the motor, it certainly will cost him much more than $37.50 to clean those injectors/carbs. Now if water or trash in the fuel caused engine damage... WOW the repair bill will be MUCH more than he will spend with Exxon all summer! And to top it all off, is it really worth the worry? The whole time he is running he will probably be thinking in the back of his mind, "Man I hope that gas doesn't hurt anything". Whether it does or doesn't I wouldn't want that worry. And man if it DID cause problems, talk about kickin yourself in the arse!!! :x
And if its premix its a double whammy, so the gas was ok (most high quality super unleadeds have enough additives and cleansers in them that storage for 6mths or so is ok.) BUT can you be positive that the fuel is clean if it was stored in a vented tank like in a boat? What about the oil that has been diluted for several months? Is it safe? Might he slightly scuff a piston because of it?
Trouble isn't worth a cheap a solution as another $37.50 worth of fuel if you ask me! EVERY year since I have owned my boat I have drained the tank completely empty each February getting ready for the fishing/boating season. It does two things, first and foremost I don't have those nagging worries like I spoke of. The second advantage is I don't need a weedeater in the first place... where do you think all that old premix goes in the first place?
RA