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Engine Efficiency

An efficient engine is not only good for the environment by minimising emissions, it will give you a better ride on the water and a less painful experience filling up at the pump!

If your engine is inefficient it will be using more fuel to power your boat and have a higher amount of emissions that impact air and water quality.


There is best practice you can adopt when operating your craft as well as the option to choose cleaner and more efficient engines  including the 4-stroke engine and electric powered propulsion compared to the traditional 2-stroke outboard engines. Although in recent years improvements have been made to the 2-stroke engine to make it more fuel efficient.


Here is an overview of 2-stroke, 4-stroke and electric powered propulsion:


2-Stoke Engines:

Traditionally 2 stroke outboard engines are powered by a two piston up and down stroke movement with both the fuel intake and the exhaust open throughout the piston’s down-stroke. This results in less control of the amount of fuel being injected into the engine and also allows fuel that has not been fully combusted to pass out into the open environment resulting in up to a 30% loss of fuel. However in recent years improvements have been made to this type of engine with technology to control direct fuel injection for example.


4-Stroke Engines

The 4 stoke outboard engines use four pistons and have a fuel and exhaust valve which are not open at the same time , resulting in a reduction in amount of fuel used to power the engine and fuel lost from the exhaust. Also the addition of two more pistons makes it heavier compared to 2-stroke engines. The 4-Stroke engine tends to be more durable and a quieter option compared to a 2 stroke engine, providing further environmental benefits by minimising noise pollution and disturbance to life above and below the water.


Electric Propulsion

A battery is used to power propulsion rather than fuel combustion, resulting in no direct emissions or concerns around oil and fuel drips and spills. Electric propulsion is also quieter helping to minimise noise disturbance and although it can be more costly to purchase compared to combustion powered engines, the running costs and level of maintenance is much lower.


If you opt for a fuel combustion engine or an electric engine there is best practice you can adopt to keep both your emissions, noise and your costs down, and to maximise the efficiency of your engine. Scroll down to find out what you can do.


  • Regularly check and service your engine. Fresh oil, clean spark plugs and dust free air-filters all help to lower fuel costs and emissions.
  • Use CE marked outboard engines manufactured after 2005 or electric engines to increase fuel efficiency, reduce noise and decrease emissions.
  • Fitting sound insulation around the engine can cut noise by 85%.
  • Vibration absorbers can also reduce structural noise by 85%.
  • Consider an electric powered craft. They have low emissions and are very quiet.
  • Try switching to biodegradable hydraulic and lubricating oils.
  • Get Planing – Whilst up on the plane the drag of the hull is reduced allowing a more efficient drive.
  • Be on an even keel – the hull needs to be as level as possible. If it is not, power and fuel will be lost trying to push the hull up rather than along. Ensure weight is distributed evenly on the craft to keep it level and provide a smoother ride and more mileage per litre.
  • Regularly clean your boat to remove biofouling to reduce drag and fuel consumption. This will also help remove harmful invasive animal and plant matter.

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