Yamalube vs. Johnson-Evenrude XD 50 Oil

[AJAK]

It was recently suggested to me by an independent marine mechanic that using XD 50 Synthetic Johnson/Evinrude oil would reduce both smoke and carbon deposits. I wonder if this is a good suggestion. Another question that I have is: Do SX 200 TXRX and LX 200 TXRX Yahama Engines shut down two (2) cylinders at idle speed?

Thanks for any help regarding the above.

AJAK