Four Stroke Outboard Smoking During Initial Start Up?

Proper storage of four-stroke outboards is critical for many reasons.  One more obvious reason for smoke during start up could be directly related to the position of the outboard during storage.  When storing four-stroke engines, either overnight or for any length of time, it's important to trim the outboards to a positive trim angle.  Here's why:

A four-stroke outboard uses a pressurized oil system that circulates oil through the engine to lubricate it.  While the outboard is running, any oil that is on the backside of the piston is pushed towardd the front of the outboard by the oil ring.  It then falls back into the oil pan to be recirculated again.  When the engine is turned off, the piston motion stops.  Any oil left on the backside of the piston is pushed toward the front if the outboard by the oil ring.  It then falls back into the oil pan to be recirculated again.  When the engine is turned off, the piston motion stops.  Any oil left on the backside of the piston typically runs to the bottom of the cylinder.

If the outboard is stored in an even or negative trim, the oil will puddle against the piston and rings.  Over time, this oil will seep past the rings and into the cylinders, thus causing the outboard to smoke on initial startup.  The appearance of smoke is normal when the oil puddles.

To stop the oil from puddling against the piston and rings, trim the outboard to a positive trim angle to allow the oil puddle to run toward the front of the outboard where it will drain into the oil pan.  Remember this simple tip, and you can avoid any smoke during initial four-stroke start up.