Outboard Engines

Outboard motors have come a long way. If you were to purchase an outboard engine prior to 2008, you would be shopping in a marketplace dominated by carbureted 2-stroke engines. In these traditional engines, the intake and exhaust ports are both open during the piston’s downstroke. They lose 20 to 30 percent of their fuel as it passes straight through the combustion chamber unburned or partially burned, releasing it directly into the water and air as pollution.

Fortunately, shifting environmental and economic concerns have generated the need for an outboard engine that is both clean and cost effective to operate. Here are more environmentally friendly outboard options:

Direct Fuel Injection (DFI) 2-Stroke Engine

The computerized DFI system precisely regulates the air-fuel mixture and directly injects fuel into the cylinder when the piston has risen up far enough to block the exhaust port. This prevents any unburned fuel from being blown out of the exhaust port. The DFI 2-stroke engine technology is not as efficient as a 4-stroke engine, but it’s much cleaner than the carbureted 2-stroke engine and reduces oil use by 50 percent.

4-Stroke Engine

In this engine, the air-fuel mixture flows into the combustion chamber via intake valves, and the exhaust leaves through exhaust valves. Both valves are never open simultaneously, preventing unburned fuel from escaping the combustion chamber and entering the environment. A 4-stroke engine is usually heavier than a 2-stroke of the same horsepower, but manufacturers continue to pursue new ways to lighten the engines.

Electric Engine

Electric motors convert battery power into propulsion. Even though electric engines are more expensive than other outboard engines, the operation costs are much lower. These engines are low maintenance, quiet, exhaust- and emission-free, and you don’t have to worry about fuel and oil spills. They are limited due to the weight and size of the batteries needed to support the engine. However, the batteries can be charged by solar panels, wind or water generators (see Renewable Energy for more information). Here are a few companies that offer electric outboard engines:

electric engines, torquedo

Green Boating Guide: