Outboard engines fall into two primary classes; 2 stroke and four stroke outboards. Each types have their advantages and disadvantages and the type you pick will rely upon the meant use. This guide will make it easier to choose which outboard engine is best on your type of boat.

2 Stroke Outboards
2 stroke engines are lighter and faster so when speed and acceleration are required, this can be the engine of choice. They're also more affordable and have a higher resale value. As 2 stroke engines have been round for nearly 80 years, parts are readily available, making repairs easy. Also, the design on these engines is less complicated than a four stroke, meaning problems are less likely to arise.
There are some disadvantages to the two stroke engine. 2 stroke engines are more pollute than 4 stroke engines so they don't seem to be so kind on the environment. Their engines are lubricated by the oil that is blended into the gasoline, that means the exhaust is smoky and incorporates unburned oil, which in turn pollutes the water.
With new regulations, outboard manufacturers are looking to find new ways of producing the same power with less pollution.


4 Stroke Outboards
4 stroke engines are quieter, smoother and more economical. Heavier with slower acceleration, they are normally chosen for lakes and rivers. With less air pollution and smoke they are also kinder to the environment. When you’re after a quieter, smoother ride, then the four stroke outboard is the better choice.
four stroke motors have more advanced engines which could lead to more repairs. When a repair is required it is usually more costly and parts are limited.
4 stroke outboards are usually heavier than 2 stroke outboards, so for those who own a smaller boat it might not be able to hold the weight of a four stroke engine.
Because 4 stroke engines are newer, they are regularly being improved to make buy and repair easier.
Some 4 stroke outboard engine producers include Yamaha, Tohatsu, Suzuki, Nissan, Mercury, Honda and Johnson outboard after market parts.
Environmentally Pleasant Outboards
If you happen to’re looking for a new outboard, it’s worthwhile considering one of the newer, environmentally pleasant models. Less air pollution, reduced noise, better fuel economy and decrease running prices are amongst the advantages.


The Mechanical Variations Between 2 and 4 Stroke Outboards
The phrases "2 stroke" and "4 stroke" refer to the number of instances the piston moves during one firing cycle of the engine. Within the 4 stroke engine, the 4 movements, or strokes, are:
Intake stroke: With the intake valve open, the piston moves down permitting a combination of air and fuel to enter the combustion chamber.
Compression stroke: The piston moves up the cylinder with the valves closed, in order that the air-fuel combination is compressed.

Combustion stroke: With the valves still closed, the fuel is ignited by the spark plug. The explosion pushes the piston down again.
Exhaust stroke: The exhaust valve opens and the piston moves up to push the exhaust gasses out of the chamber so the process can be repeated.
In a 2 stroke engine, there are only two movements of the piston for every combustion; one up and one down:
Combustion stroke: Combustion of fuel drives the piston downwards. As the piston moves down, it exposes an exhaust vent and fuel inlet in the wall of the cylinder allowing exhaust gasses out, and new air and fuel to be sucked in.
Compression stroke: As the piston moves back up, it blocks off the exhaust vent and fuel inlet and thus compresses the air/fuel mixture. The spark plug ignites the air and fuel inflicting the piston to move down again.
The fuel inlet and the exhaust vent within the wall of the cylinder eradicate the need for valves and the mechanism for opening and shutting them which is why 2 stroke engines are a lot simpler in design.

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