I want to switch from petroleum 2 stroke oil to a synthetic 2 stoke oil to reduce the smoking. I did this with my outboard motor but needed to change the oil to gas ratio.

Synthetic may help but I'd caution you about altering the oil gas ratio. Your engine may be smoking for other reasons and the new ration may not provide the lub protection your engine needs.

Try opti II all mix .
Mixes all ratios and no smoke.
Luck