Basics of Outboard Engine

It requires a fuel/air mixture that has to be delivered to the cylinder, inside the cylinder the mixture gets compressed and ignited, when it’s done burning the exhaust gases inside the engine must be removed.

Both the four-stroke and two-stroke is comprised of four essential steps to work properly.

The piston valve inside the cylinder travels down to suckthe air-fuel mixture behind it.

The piston compresses the mixture to make an efficientexplosion. Relatively piston rings stop the mixture from leaking out through the sides.

Four-stroke

Now the piston is pushed back to its original position andreleases the burned gases to start the cycle all over again. Thus it converts the reciprocating motion of the piston into a rotary motion.

The compressed mixture is now ignited and the resulting explosion forces the piston down the cylinder.

Here the pistons moving alternately reveal and cover-up ports in the cylinder walls,thus it acts as valves. The ports act as a gateway for the gases toenter and exit the chamber.

Two-stroke

The significant difference here is the absence of intake and exhaust valves.

In the two-stroke engine the intake and compression arecombined into one operation and the power and exhaust stroke into another.

Thus two-stroke engine completes all four necessary functions such as intake, compression, ignition, and exhaust with two strokes of the piston within the cylinder.

Two-stroke outboard enginesdon’t have crankcase oil. Also,it works well without the valves but the problem with this is lack ofefficiency and high pollution rate.

Hence, the revolution of the crankshaft is one instead of two.