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Two stroke and 4 stroke outboard engines are the two main categories that exist in the motor world. There are pron and cons that come with each, so you need to choose based on what you need your engine to do. Below are some helpful points that will guide you in making your decision.

2 Stroke Outboards
When you want speed and acceleration, a 2 stroke engine is the right choice because they are lighter and faster. The resale value of 2 stroke engines is greater than 4 stroke, and they sell for cheaper new. Also, since they are so common, finding spare parts for repairs is relatively easy. Need for said repairs is infrequent due to their simple design.

Environmental friendliness, or better put lack of it, is the main disadvantage to the 2 stroke engine. Because they are lubricated with gasoline mixed with oil, the exhaust is very smoky and pollutive. This is because there is unburned oil in it. New green laws have manufacturers such as Mercury, Nissan, Yamaha and Evinrude scrambling trying to develop a cleaner engine with the same power.

4 Stroke Outboards
Although slower and heavier, 4 stroke engines are quieter, smoother and more economical. This makes them a perfect choice for lakes and rivers. They are more eco-friendly producing less pollution and smoke. Since they are more complicated, 4 stroke outboards with their greater number of parts often require more frequent repairs. The repairs are generally more expensive too, but with manufacturers such as Johnson, Honda, Mercury, Nissan, Suzuki, Tohatsu and Yamaha, continually improving them, repair is getting easier. The other major drawback is the weight. Not all boats can handle the 4 stroke engine.

Environmentally Friendly Outboards
Less pollution, reduced noise, better fuel economy and lower running costs are just a few of the advantages in purchasing an newer model of outboard motor. They are also environmentally friendly.
The Mechanical Differences Between 2 and 4 Stroke Outboards
The terms "2 stroke" and "4 stroke" originate from the number of piston movements during one firing cycle of the engine. In the 4 stroke engine, the four movements, or strokes, are comprised of the:

Intake stroke: A mixture of air and fuel to enter the combustion chamber through the intake valve as the piston moves down.
Compression stroke: The piston compresses air-fuel mixture by rising
up in the cylinder.

Combustion stroke: With closed valves, the spark plug lights the fuel causing an explosion that pressed the piston down again.
Exhaust stroke: The exhaust valve opens to allow the exhaust gasses out of the chamber and the piston rises to begin the process again.

There are only two movements in a 2 stroke engine; one up and one down:
Combustion stroke: The explosion of fuel launches the piston downward. In the process, it uncovers an exhaust vent and fuel inlet in the wall of the cylinder. These permit exhaust gasses out, and new air and fuel to be sucked in, respectively.

Compression stroke: When the piston ascends, it covers the exhaust vent and fuel inlet in order to compress the air/fuel mixture. The piston is forced back down again when the spark plug ignites the air and fuel.
The design is much simpler because there are no need for valves or a device to open and close them.

David has been writing online for a while now and loves outboard engines, however he also writes about computer desks. Check out his sites: Used Outboard Engines and Computer Table Desk.