Most modern outboards mix at 50:1
From the mix bottels you get at the store that is 16 ounces of oil to 6 gallons. If you do the math , that is a little richer than 50:1 but this is a general rule of thumb.
Do not use cheep oil!!!!
Use Yamaha outboard oil or an other oil like Mercury or Evinrude outboard oil.
The other off brand oils clame to have the lubricating properties but they may leave carbon in the cylinders and then you will be rebuilding the motor soon after that.
I'm a professional boat tech.