The 2-stroke engines are used for vessel propulsion and are bigger in size as compared to the 4-stroke engines. In this engine, the complete sequence is complete in two cycles i.e.
Suction and compression stroke – which is the upward movement of the piston to draw fresh air inside and to compress the air-fuel mixture
Power and exhaust – which is the downward movement of the piston due to an explosion inside the chamber followed by the removal of exhaust through the exhaust valve fitted on the top of the cylinder. A stuffing box is used which separates and seals the crankcase against the combustion chamber
2 stroke engines typically have a higher power-to-weight ratio, which makes them ideal for use in smaller marine vessels where weight is a concern. These engines tend to produce more pollution and noise compared to 4-stroke engines, and they may not be as fuel efficient.