My oil experience has only involved two oils. Royal purple fully synthetic oil @ 50:1 and Pennzoil Semi-Syn
50:1. The smoke is equal between the two but the smell and cost are not. The RP had a terrible smell to it as it burns (really the wrong oil for a pre-mix carbed outboard), and burned your eyes in the driveway. The pennz gives off a sweet smell.
Regardless they both would smoke for 30-45 seconds on first fire of the day. and for 5-10 seconds on restart. Other then that, no smoke visible during running while on the water.
In a pre-mix situation, do not waste the cash on synthetic. The semi-synthetics do a great job at keeping the cost,smoke,carbon down while giving you great protection. I would run synthetic in any direct injection, fuel injected etc engine as it is a precised metered system.
I agree with Jim and 82Rude about the Evinrude oil, I have heard they are amazing oils for outboards. XD30 is cheapest, XD50 would be ideal. Bringing an empty jug to a dealer will net you around $25 for XD30 and $35 for XD50. You will still see smoke with these premium oils on a carbed outboard.
I recommend a decarbon via dunks method and a switch to pennzoil semi synthetic 50:1.