Outboard Engines

Many small engines, such as conventional two-stroke engines used in marine outboard and personal watercraft, are high polluters relative to their engine size, emitting a range of toxins into the water and the air. As substantial power is required to move small craft through water, even the better performing engines can emit far greater quantities of pollutants per hour than typical modern car engines.

A recent comparison of a conventional 15 horsepower carburettor two-stroke outboard and a 150 horsepower fuel-injected four-stroke outboard found that the smaller engine produced three times the emissions of the larger engine.

To help boat owners choose outboard engines based on comparable emissions, Outboard Engine Distributors Australia (OEDA) has implemented an emissions ratings system known as the Voluntary Emissions Labelling Scheme (VELS) for sales of new outboard engines, similar to energy and water efficiency ratings schemes for household appliances (see the VELS table below).

Responsible Reef Practices

• Consider purchasing a new, cleaner running marine engine
• Choose ultra low emission engines and use the OEDA VELS as a guide (see table below)
• Ensure that your outboard engine is kept in good condition and is serviced according to the manufacturer's recommendations
• Properly match engine horsepower to the size of the vessel
• Use the right size propeller and keep it in good condition (nicks and dents reduce performance)
• Drive your boat conservatively. Abrupt starts, excessive speed and extended use of full throttle not only reduce fuel efficiency and increase emissions, but are also hazardous to slow moving marine animals such as dugong and turtle
• Properly trim your boat whilst underway
• Reduce unnecessary engine idling
• Reduce weight. Extra cargo in your boat reduces fuel efficiency.
  

VELS star ratings

 * The OEDA Emissions Limits rate engines based on Hydrocarbon (HC) and Oxides of Nitrogen (NOx) emissions, measured in grammes per kilowatt per hour.