ALWAYS INCLUDE THE YEAR/MODEL/SERIAL#
Usually just a good cleaning works.
UNLESS!!!!! there's a lot of CRUD built up in the float bowl.
The bowl, the fuel settles in it and congeals and can cause problems.
If the bowls nasty??? then it's a good chance the air/fuel passages are nasty too
Stay away from 91 and Seafoam.
91 burns too hot and it's like adding soap if you put in SF.
SF is WAY over rated.
Want a good cleaner, Mercury, OMC and Yam all have carbon removers.
Mer-is Power tune, OMC Engine tuner Yam (not sure of the name).
Get it and follow directions.
Outboards and excessive smoke.
Every time the motor turns over and doesn't start/run.
The motor draws fuel/oil in and if it doesn't burn?? then the gas evaporates and the oil just builds and builds.
Then when(???/if) it starts a cloud of smoke and instant mosquito fog.
Getting it up to temp will burn off the excess oil.