V8 5.6-liter F425

The large-displacement 5,559 cm3 60° V8, 32-valve DOHC four-stroke engine is packed with features. These include a direct fuel injection that uses a very high fuel pressure sprayed via robust fuel injector that directly enters into the combustion chamber. Outstanding atomization of the fuel spray greatly increases the effectiveness of the fuel burn for maximum power and fuel efficiency. Dual overhead camshafts on each cylinder bank are connected via a self-tensioning chain immersed in an oil bath. Quiet, precise, and maintenance-free connection for proper and consistent valve timing.

Maximizes power and efficiency by spraying fuel at high pressure directly into the combustion chamber. It's the first four-stroke powerhead in the outboard industry to feature direct injection.

A three stage fuel pump system (low, medium, and high) that ultimately delivers very high fuel pressure to direct fuel injectors that spray directly inside the combustion chamber. Stable output is maintained by supplying fuel with an appropriate compression ratio.

Allows draining and replacement of lower unit lubricant without having to remove the boat from the water. Maintainability has been increased by allowing the user to work on the boat without removing it from the water.

Fully electric steering is the first of its kind in outboards. Uses an electrical motor to directly move and secure the outboard, rather than using hydraulics and an electric pump (known as electro-hydraulic steering). Very fast, precise, responsive, leak-free, maintenance-free, and uncomplicated, fully electric steering makes for reduced power consumption, clean rigging, and a very orderly bilge area. Reductions in electric power consumption result in reductions in fuel costs.

Diverts engine exhaust away from propellers at rpm below 2,500, allowing for maximum command and control at low speeds. Also greatly increases the effectiveness of the Yamaha Helm Master fully-integrated boat control system.

Unique to Yamaha’s Offshore XTO outboard, the cowling and engine covers are integrated via fasteners and a special one-piece seal to allow easier access to specific portions of the powerhead and mid-section while preventing water intrusion and corrosion.

A sophisticated and powerful engine management system controls the isolator charging circuit, power trim & tilt (PT&T) operation, ETV, DI, Fuel Pumps and Main relay, etc.
Each system can be centrally controlled, allowing each component to be maintained and warning signs to be seen at early stages.

To address the potential of any “residual” heat buildup, a very effective rotary cooling fan was developed and integrated into the motors flywheel. Basically, whenever an F375A/F425A is running, air is continually being drawn from the “flywheel/stator” area of the motor, and ducted to an exit at the front of the upper motor cover (as illustrated). Even at low engine speeds, this innovative cooling system is still very effective at drawing heat from the flywheel area of the motor.

A newly designed lower case is itself larger while offering enabling higher maximum speeds and greater stability. Additionally, durability and anticorrosion properties have been improved by redesigning the passages in which oil moves inside the case and utilizing stainless steel components. Furthermore, a new gear-oil replacement system allows gear oil to be changed while the boat is moored.

This revolutionary, totally electric, steer by wire unit is completely contained on the outboard. Silky smooth operation is accomplished with virtually effortless steering inputs. Other benefits of SBW include:

• Attractive, and very clean appearance.
• Minimal maintenance required.
• Has faster steering response times than typical hydraulic systems.
• No separate modules, steering pumps, hoses or interconnecting harnesses.
• Simplified installation, with never any fluids or air to purge.
• Allows 7 degrees more tilt “Up” angle (when compared to F350 models).
• Energy efficient, with greater durability against the harsh marine environment.

Additionally, each engine constantly monitors the position of the permanent engine when in multi-engine mode, the system thus controlling all components to ensure sufficient distance between engines.
Furthermore, this is a dual-system-monitoring system, meaning that the boat can be maneuvered with the backup system even in the rare event that a malfunction occurs. Even if a malfunction that precludes steering occurs, the design permits the rudder to be adjusted manually.
Thus, the system provides stable, reliable steering that can be configured for various conditions the boat might encounter.