Quick Tip: Smoke Signal

Four-Stroke Outboard Smoking During Initial Start Up?
Here’s a Storage Tip that Can Help

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 Yamaha 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 toward 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 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 start up. The appearance of smoke is normal when the oil

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.