Re: feul mix
Some where back in the 80's OMC(Evinrude/Johnson) ran a 100:1 but due to Cheaper fuel and lack of use, they recommend switching to
50:1
That equates to ~2.5-2.6oz of oil to 1 gallon of gas. (I would go with 2.5 oz of GOOD TWCIII oil, Not "Bob's" oil) The best Oil is a full synthetic, it burns much cleaner and more moister tolerant. The next best would be a synthetic blend.
Anyway for 20 gallons you mix 50oz of oil
McG