Yamaha V8 425 XTO Offshore direct injection outboard.

In recent years the demand for boats using outboard engines has grown enormously. In the past the use of these engines was limited to pushing boats with a maximum length of around 10 meters, now these boats can easily reach 15 meters. Also because with the development of technology the outboards are always more powerful with lower consumption and the attention is maximum to make them always lighter. The choice of the type of diesel or petrol outboard may depend on the type of boat you want to power and the number of miles you want to sail.

In addition the outboards do not require a machine room and two, three and even four or more large outboards can be mounted on a sturdy bracket at the end of the transom and at the same time increase the usability of the boat spaces.

Furthermore, it is possible to fully customize your boat by selecting not only the power but also the type of outboard to be installed.

A trend that started in America where the market is more flourishing and then spreading to the rest of the world.

The choice of the type of outboard is a rather important feature both to equip a pleasure boat and a high performance one.

Obviously the manufacturers of outboard engines have seen this trend stand out and have started developing ever bigger engines.

At present there is a great competition among the big builders with a real challenge not declared but evident and the goal is always the same to build, in the various power classes, the most powerful and reliable outboard engine and the most technologically the most evolved of the moment to satisfy an increasingly demanding clientele.

The V8 425 XTO Offshore with the incredible power of 425 horsepower is the new Yamaha engine for this type of fast growing market.

This engine was designed primarily to offer a huge torque of 542 Nm which produces a great thrust already 2,000 rpm useful especially in the moment of gliding with propellers designed and built to push large hulls.

Therefore, it is rightly a candidate, also through applications involving multiple engines, to power large boats, large dinghies and RIBs with a certain consistency and length that until recently were powered by huge sterndrive or inboard engines.

The V8 425 XTO was launched on the market at the end of 2018 so just a year ago in response to the Mercury Verado 400R supercharged outboard engine. Meanwhile, the competition has not long been waiting for a distance of just twelve months Mercury reacts with its new outboard this year 2019 the Verado 450R , this only to highlight the strong competition that exists in the sector.

But each engine has its peculiarities, the most important for V8 425 XTO Offshore, which sets it apart from the competition, is the first 4-stroke marine series production engine with direct petrol injection.

In fact it has 8 cylinders arranged in a V shape characterized by a narrow angle of 60 ° 4-stroke 5.6-liter double shaft accommodates the direct injection of petrol at an impressive pressure of up to 2,900 psi.

This is thanks to an innovative feeding system called DFI which sprays high-pressure fuel directly into the combustion chambers, to significantly improve atomization and thus produce a perfect homogenization in the mixture of area and petrol for maximum power and efficiency.

Furthermore, by using this system there are fewer exhaust emissions, greater fuel savings, especially at low speeds, and the ability to perfectly match the fuel delivery to the engine load which boasts an incredible compression ratio of 12.2: 1

Yamaha states that the fuel system of its V8 425 XTO requires five separate fuel pumps to reach 2,900 psi or 200 Bar.

A new exhaust system has been developed on this engine that facilitates mooring maneuvers. At low speeds the exhaust gases are expelled through a series of air intakes positioned above the anti-cavitation plate not through the propeller hub and this makes it easier to reverse or push the propeller backwards. Only when the engine speed exceeds about 2500 rpm does the exhaust exit through the propeller hub.

It is not just an engine but an entire propulsion system integrated with the wheelhouse which is another innovation of the new V8 425 XTO because the first outboard motor in the world to have it is completely electric. There is only one connection from the electronic rudder to the engine and no hydraulic system in the boat or on the engine, the steering system is contained in a tube-shaped device in the front of the outboard and according to Yamaha it provides a faster response to the inputs of the steering and better control.

In addition, the electric system weighs 38 kg less than its electro-hydraulic systems and saves a lot of space in the transom.

The current on the boat is always ensured because the alternator supplies sufficient current even at low speeds until it reaches 90 A at higher speeds. The oil is changed without lifting the boat from the water directly to the mooring with a real economic advantage through the Yamaha’s patented oil replacement system.

Other and numerous technical innovations are integrated in the new Yamaha V8 425 XTO Offshore. Like the new propellers designed and built to complete and implement the enormous torque potential that ensure more thrust in both travel and reverse than the smaller Yamaha F350 and thanks to the new exhaust gas system, these propellers have another advantage, at low speeds without exhaust on the propeller hub, they “bite” clean water in reverse, facilitating the production of a reverse thrust three times greater than that developed by Yamaha’s F350 and this facilitates maneuvering and control during mooring especially for applications with multiple engines managed by joysticks, since there is a greater opportunity to balance the thrust between the engines that work in forward and reverse.

In this regard Ben Speciale the president of Yamaha Marine issued the following statement:

“The F350 outboard taught us that outboard motor boats could become much bigger.” “To push a bigger boat we have to start with a bigger propeller. And to shoot that propeller, a lot more torque. “

Everything about the V8 425 XTO is oversized to the detriment of weight.

Like the gearbox with hardened gears, the two-stage water pump, a double-chamber oil pump, special iridium spark plugs for longer life and more. Not forgetting the weight of the electric steering system installed in the outboard is therefore included in the overall weight of the engine.

V8 425 XTO is available in the 25, 30 and 35 inch shaft versions.

The 25-inch shaft version weighs 432 kg (952 pounds), the 30-inch unit weighs 443 kg (977 pounds) and the 35-inch model weighs 453 kg (999 pounds) and this is a dry weight without propeller and without engine oil.

These weights may seem high for an outboard motor, if compared for example with the same Yamaha F350 weighing 346 kg or with direct external competition, of the same power class, such as the Verado 400R Mercury weighing 303 kg and the new Verado 450R Mercury weighing 313 kg.

The Yamaha does not seem to worry about the weight, as it affects very little compared to the total weight of the boat and in any case the V8 425 XTO was not designed to be the lightest outboard in the 400 hp power class, but to be the best outboard thrust for large pleasure boats equipped with two, three, four or more outboards that integrate perfectly with the updated control system of the Yamaha Helm Master joystick boat.

It should also be remembered that these engines will replace inboard or inboard gas and diesel engines with enormously higher weights. That will work on boats that weigh around 30,000 pounds (13.608 Kg) where the net weight of the engine will not be a problem because the influence is minimal compared to the weight of the boat. Pair, trim, propeller size and access to the boat these will be the main problems.

From a sea trial done on an 11-meter boat that fitted a triplet of 425 XTO V8 engines with a total weight, including engines, of 8,000 kg it was found that with 54 knots the consumption was around 75 liters per mile, consumption dropping sharply to 4.3 liters per mile with a cruising speed of around 29 knots.

From another test made this time on a maxi inflatable boat equipped with 4 V8 425 XTO engines, 15 meters long and weighing a total of 11,000 kg, the following was found:

2,400 rpm speed 14.7 knots the boat was already gliding;

3,000 rpm speed 22 knots – consumption 120 liters per hour;

3,400 rpm speed 25 knots – consumption 150 liters per hour;

5,000 rpm speed 42 knots – consumption 400 liters per hour

At higher speeds consumption was not detected.

However, these measurements are sufficiently comprehensive to establish that they are of excellent performance considering the weights of the boats and the power of the engines at the ends of the stern mirrors of the two vessels.

The engine is available both in the classic gray Yamaha color and in pearl white or without paint to then be colored according to the customer’s taste coordinated with the colors of the boat The base price for an extra long engine (30 inches) is about 62,000 dollars.

Main technical features

Displacement: 5,559 cc;

Bore x stroke: 96 × 96 mm;

Power: 425 hp;

Double camshaft distribution: 32 valves;

Power supply: DFI direct electronic injection;

Alternator: 90 A.

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