The fact that outboard motors must be compact and light in weight has, of course, meant that light and compact two-stroke machines have constituted the mainstream. In recent years, however, concern about the global environment has resulted in increased attention being given to four-stroke configurations to achieve low vibration, low noise, clean exhaust, and high fuel efficiency.
Yamaha's "F50A" outboard motor has many unique mechanisms designed to meet these needs. Among them are a low-noise mounting device to restrain vibration, a resonant silencer to suppress noise, and a blow-by gas recombustion system to keep the exhaust clean. It is a quiet, clean and economical product that takes full advantage of the positive features of the four-stroke principle.
Moreover, the straight four-cylinder, long-stroke engine is equipped with four precision carburetors with an acceleration pump, which, together, give engine performance that is far superior to that offered by conventional four-stroke machines.
The F50A has several important features that add up to high durability. The engine body is built of a highly corrosion-resistant aluminum alloy (YDC-30) that was developed by Yamaha on its own. It is coated in five layers; and it is protected with five different corrosion-preventive systems, including a self-sacrificing anode. This is truly a state-of-the-art four-stroke outboard motor.
Specifications
Yanmar Diesel Engine Co., Ltd.
Yanmar Marine Diesel Engine 4LH Series
The amazingly compact LH-A triumph of technology
The LH introduces a futuristic low-line design that makes the cylinder head cover the highest point on the engine. The high power configuration puts the 4LH series engines into world-class standing in all three main areas of comparison: namely, more horsepower per unit volume, more power per unit displacement, and more output per kilogram of engine weight - up to 169kW in a compact package.
The engines' slim configuration makes for easy installation, even in tight locations. Repowering becomes easier, new boat designers can choose more horsepower, or a roomier engine bay, and the fore-and- aft balance is significantly improved.
The 4LH series engines also offer all the benefits of Yanmar's commitment to protecting the environment. This includes such features as low noise, low vibration, and superior fuel economy. The engines are precisely controlled with high-pressure fuel injection to reduce emissions and to keep smoke at a very low level, especially when accelerating or idling. Vibration is also reduced by the use of special steels in the block and other critical areas.
The 4LH-TF is turbocharged, and the 4LH- HTE/DTE/STE are quipped with turbochargers and air-intercoolers. All have direct injection and heat exchanger cooling.
