More boat owners want big outboards for their cruising boats, and Yamaha has delivered, just unveiling a new 425-hp V-8, its most powerful ever. Yamaha says this new engine features the first application of direct injection technology in a four-stroke outboard; this sprays fuel at high pressure directly into each combustion chamber, rather than the intake track, providing more efficiency, power and torque with faster acceleration and a higher top speed.
The new outboard also is the first time Yamaha has used sleeveless cylinders, formed through plasma fusion technology, and iridium spark plugs for reliability and durability. The company says the combination of a new exhaust-gas relief system and newly designed propellers provide more torque for cruising but also for reserve thrust.
The 5.6 liter engine runs on 89 octane fuel, and has two thermostats per cylinder bank to make sure it maintains proper temperatures; one pair regulates the engine temperature, the other two maintain oil temperature.
For easier servicing, the lower-unit gear lube can be changed while the boat is still in the water, and the engine can be tilted higher on the transom than the Yamaha 350. Yamaha also has developed two methods for flushing the outboard: one through the rigging tube and the other through the usual front-mounted hose connection.
Yamaha says it wants to become “an integrated system supplier,” so it has developed a new Integrated Electric Steering System for the new engine, eliminating the need for cables or hydraulic lines. This system also features Yamaha’s Helm Master joystick control for fingertip maneuvering at low speeds.
The new engine is available in white, gray, or unpainted, and comes with a five-year warranty. For more:
https://global.yamaha-motor.com/news/2018/0523/f425.html
