Yamaha reinvents its V6 four-strokes

Yamaha's latest range of outboard motors features a new engine and a new manufacturing process, Mike Rose reports

In the United States, they are apparently referred to as the "game changers" although exactly where the phrase came from is unclear.

What is clear is that with its new V6 four-strokes - their new 300, 250 and 225 horsepower models - Yamaha appears to have achieved the golden troika of lighter engines that are also both stronger and faster.

At the heart of the change is the new engine, a 4.2-litre 60-degree V6. It features double overhead camshafts with variable camshaft timing.

It also, and this appears to be the key, features what Yamaha calls a "highly-advanced plasma fusion process" on its cylinder walls. According to their literature, the cylinder walls in these new V6s are 60 per cent harder than steel.

This has allowed Yamaha engineers to create larger cylinder bores, and therefore more displacement, without having to increase the size of the engine. In other words, the engines produce more power and torque but are no bigger and no heavier.

The new engines are not only not heavier than their predecessors, they are actually lighter. All three of the new models, including the F300, weigh less than Yamaha's current 3.3 litre F225, already a lightweight in its class.

In a trend that is becoming increasingly common, the new four-strokes are comparable in weight to the company's direct injected two strokes. Considering the new models offer substantially larger capacity, this is no mean feat.

Yamaha says the new plasma fused cylinders also result in better cooling and feature "micro-textured" cylinder walls to help decrease friction and further increase performance and reliability. The engines' greater capacity, and therefore greater output, has also allowed Yamaha to use a lower 1.75:1 gear ratio, allowing the new V6s to spin a larger propeller.

"The result," says Yamaha's New Zealand marine manager, Greg Fenwick, "is better hole-shot performance. As well, the engines' variable camshaft timing delivers crisp acceleration and great fuel economy right through the rpm range."

The new F300, F250 and F225 also feature "drive by wire" control systems for smoother throttle operation, more responsive performance and more secure and reliable gear shifting. Fenwick says the engines also feature a patented shift dampening device that eliminates the noise that sometimes occurs when engines are shifted in and out of gear.

The V6s are also compatible with Yamaha's new instrumentation. This comes in the form of a 5-inch colour LCD screen capable of displaying information from both the outboard and the boat. It can also connect to and display information from up to three engines.

Yamaha's new V6 range will be available in New Zealand from June. They will come with 25in or 30in shafts and counter rotation models will also be available for multi-outboard installations. Yamaha's four-stroke full 4-year manufacturer's warranty will also apply.

YAMAHA V6 4-STROKES

Models: F300, F250, F225

Full throttle range: 5000-6000rpm

Dry weight with prop: 258kg

Engine type: 24-Valve, DOHC w/VCT, Direct action, 60 deg V6

Displacement: 4169cc

Bore x stroke: 96 x 96mm

Compression ratio: 10.3

Gear ratio: 1.75:1