Here are some factors to consider:
* Emissions:
* EPA Tier 3 Certification: Most modern outboard engines meet the latest EPA Tier 3 emissions standards, which significantly reduce harmful pollutants like hydrocarbons, carbon monoxide, and NOx.
* Four-stroke vs. Two-stroke: Four-stroke engines generally produce fewer emissions than two-stroke engines, especially older models.
* Fuel Injection: Fuel-injected outboards generally burn fuel more efficiently, resulting in cleaner emissions.
* Electric Outboards: Electric outboards produce zero emissions while running.
* Fuel Efficiency:
* Fuel Injection: Again, fuel-injected engines tend to be more fuel-efficient than carbureted engines.
* Engine Size and Propeller: Choosing the right size engine and propeller for your boat can significantly impact fuel efficiency.
* Oil Consumption:
* Four-stroke engines: Typically use much less oil than two-stroke engines.
* Direct-injection technology: Some newer two-stroke engines have direct-injection technology, which reduces oil consumption.
* Noise Pollution:
* Four-stroke engines: Generally quieter than two-stroke engines.
* Electric Outboards: Very quiet.
Here are some brands known for their clean-burning engines:
* Yamaha: Known for their fuel-efficient four-stroke engines and focus on clean technology.
* Honda: Another well-respected brand with a wide range of clean-burning four-stroke outboards.
* Mercury: Offers both four-stroke and two-stroke engines, including fuel-injected models with advanced emissions control.
* Suzuki: Known for their fuel-efficient four-stroke engines.
* Torqeedo: A leading manufacturer of electric outboards, offering zero-emission propulsion.
Recommendations:
* For best overall cleanliness: Choose a four-stroke, fuel-injected engine from a reputable manufacturer like Yamaha, Honda, Mercury, or Suzuki.
* For the cleanest possible solution: Consider an electric outboard like those from Torqeedo.
Ultimately, the best "cleanest burning" outboard for you will depend on your specific needs and priorities. Do your research, compare options, and consult with a reputable marine dealer to find the right engine for your boat.
