Outboard engines fall into two essential categories; 2 stroke and 4 stroke outboards. Both types have their advantages and disadvantages and the type you pick will depend upon the intended use. This guide will make it easier to select which outboard engine is best to your type of boat.
2 Stroke Outboards
2 stroke engines are lighter and faster so when speed and acceleration are required, this could be the engine of choice. They are also more affordable and have a higher resale value. As 2 stroke engines have been round for nearly eighty years, parts are readily available, making repairs easy. Additionally, the design on these engines is less complicated than a four stroke, which means problems are less likely to arise.
There are some disadvantages to the 2 stroke engine. 2 stroke engines are more pollute than four stroke engines so they don’t seem to be so kind on the environment. Their engines are lubricated by the oil that’s blended into the gasoline, which means the exhaust is smoky and accommodates unburned oil, which in turn pollutes the water.
With new laws, outboard producers are looking to seek out new ways of producing the identical power with less pollution.
4 Stroke Outboards
four 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’re also kinder to the environment. Should you’re after a quieter, smoother ride, then the 4 stroke outboard is the higher choice.
4 stroke motors have more advanced engines which could lead to more repairs. When a repair is required it is normally more expensive and parts are limited.
four stroke outboards are usually heavier than 2 stroke outboards, so in the event you own a smaller boat it will not be able to hold the weight of a four stroke engine.
Because four stroke engines are newer, they are regularly being improved to make buy and repair easier.
Some 4 stroke outboard engine producers embody Yamaha, Tohatsu, Suzuki, Nissan, Mercury, Honda and Johnson outboard after market parts.
Environmentally Friendly Outboards
For those who’re looking for a new outboard, it’s worthwhile considering one of the newer, environmentally pleasant models. Much less air pollution, reduced noise, higher fuel financial system and decrease running prices are amongst the advantages.
The Mechanical Differences Between 2 and four Stroke Outboards
The phrases «2 stroke» and «4 stroke» refer to the number of occasions the piston moves during one firing cycle of the engine. Within the 4 stroke engine, the four movements, or strokes, are:
Intake stroke: With the intake valve open, the piston moves down allowing a mixture of air and fuel to enter the combustion chamber.
Compression stroke: The piston moves up the cylinder with the valves closed, so that the air-fuel mixture 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 might 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: Because 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 causing the piston to move down again.
The fuel inlet and the exhaust vent within the wall of the cylinder eliminate the necessity for valves and the mechanism for opening and closing them which is why 2 stroke engines are much simpler in design.
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