Choose the right type of engine for your boat. The weight and horsepower of your engine will have an impact on your boat's performance. Most good dealers will guide you through these choices, but knowing what questions to ask is critical to getting exactly what you want.
Outboard engines are mounted on the stern or outside of the hull. The gearbox and propeller of an outboard engine are submerged in the water during operation, but can be tilted out of the water when not in use. This prevents unwanted corrosion or marine growth and makes them ideal for salt or fresh water use.
In the past, outboards were typically conventional two-stroke engines, but manufacturers have since moved to environmentally friendly, low-emission engines, including direct fuel injection (DFI) two-stroke and four-stroke designs.
The new outboards meet stringent new EPA emissions regulations, which also help make them more fuel-efficient than earlier outboards. Some manufacturers use four-stroke engine designs, while others use a modern two-stroke design called direct fuel injection (DFI). Modern low-emissions marine outboard engines run quieter and smoother than engines from 15 years ago, with virtually smoke-free exhaust.
Carburetors are the most basic type of fuel intake system and are a cost-effective way to control the delivery of fuel to the engine. However, some modern 4-stroke outboard engines with carburetors are calibrated to meet all applicable exhaust emission standards, providing much better fuel economy than older 2-stroke carbureted engines.
Fuel is injected directly into the combustion chamber and ignited by spark plugs. The highly atomized fuel spray from the injectors rapidly reduces the temperature of the combustion chamber, resulting in higher engine power, lower fuel consumption and lower emissions. Direct fuel injection provides fuel-free starting, fast engine starting and precise engine speed and performance throughout the engine's operating range.
Fuel is injected into the intake air of each cylinder, just before the engine's intake valves. The fuel spray from the injector contacts the hot intake valves, cooling the valves and increasing the vaporization of the fuel before it is introduced into the combustion chamber. The spark plug then ignites the fuel-air mixture. The advantages are fast engine start, low emissions and fuel consumption, and strong engine performance.
Marine gas engines are automotive engines adapted for use on the water. Gasoline stern drive and inboard engines range from 135 horsepower per engine to over 1,000 horsepower per engine and can be used on a variety of vessels.
Inboard engines have the engine and transmission mounted below deck on the hull. The drive shaft extends through the hull and the propeller is mounted on it to drive the engine. Steering is accomplished through the use of a rudder.