2 strokes are extremely inefficient when it comes to combustion at low rpms.
Up to 40% of the fuel/oil mix is blown out the exhaust port.
That blue smoke is unburnt oil. If you run your oil mix too rich,
or are choking the outboard, you'll get the same results.
They aren't called "2 smokes" for nothin'.
To learn about the choke knob, take the cover off your outboard.
Remove the intake cover off the carb, turn your choke knob one direction.
If the butterfly plate rotates and opens the throat of the carb
then you've turned the choke off. If it blocks the throat
then you turned the choke on.
It's extremely important to get the oil/fuel mix correct.
50:1 mix is almost exactly 2.6 ounces of 2 stroke oil per gallon.
Measure when you mix, otherwise too much and you lose power,
too little and you can do severe damage to the internal working components.