Sludge has been a star of gasoline ads for the last several years, but do you even know what it is or why you need to be protected against it. Oil will oxidize over time, and when this happens the additives in the oil separate out. These additives consequently breakdown and solidify, then are heated and turned into a gooey, viscous substance we now refer to as sludge.
The obvious question is how do you get rid of and prevent sludge; and unfortunately there’s no easy answer. Flushing the engine can be effective, but you also risk simply flushing the pieces of sludge to a more recessed part of the engine. The best way to handle sludge is by preventing it in the first place. You can do this by changing your oil regularly and only using premium products like Evinrude or Yamaha oil.