I would imagine 12:1 fuel ratio would be very hard to crank, and if you did get it to crank, it would leave a very oily trail behind the boat.
With modern two cycle oils you could easily get away with using as little as 32:1 fuel/oil mix, but the best mix for the environment and still be good for the motor would probably be around 24:1.
Looking on the tables on Jason's website, the original mix was 3/4 pts. SAE-30 per gallon of gas. outboard 2 cycle oils are much better at lubricating than the old motor oils could.