I had a 2004 oil-injected Yamaha that smoked like any ole' 2 stroke does. I had been using Yamalube as thats what came with the motor.

I ran out of Yamalube so I tried Pennzoil synthetic outboard oil and found that the smoke did decrease. It didn't go away completly but it was definatly better.

After using the synthetic for a couple tankfulls I found that the motor also started faster than with the Yamalube.

I got a bigger boat and went with a 4 stroke Yamaha 150 and Yamaha 8. I will NEVER,EVER own another 2 stroke. Its so nice to be able to fish all day and not have a headache from a cloud of blue smoke.