At some point, every outboard motor smokes. To reduce the amount of smoke and the frequency in which it appears there are a few steps responsible boat owners can take. The first step is to add fresh fuel to the fuel tank.
The next step, and perhaps the most effective, is to change the motor’s oil. Replace old mineral oil with synthetic oil, like the Evinrude 2 cycle oil XD100. Synthetic oil runs cleaner, thus immediately reducing smoke. De-carbonizing the outboard motor also reduces the carbon build-up that causes smoking and poor performance.