350hp Yamaha V6 Offshore outboard engine revealed

The new engine is built on a 4.3-litre V6 running a 11.1 compression ratio to extract more performance. Weight is 250kg for the lightest version, the same as the Yamaha F300 on which this engine is based. This compares with 329kg for Suzuki’s 4.4-litre V6 DF350, 316kg for Mercury’s 5.7-litre V10 Verado, and 347kg for Honda’s new 5.0-litre V8 BF350.

The new V6-based F350 replaces the 60-degree banked 5.2-litre V8 version introduced in 2007.

It is also fully fly-by-wire, featuring built-in electric steering and integrating with Yamaha’s digital shift and throttle controls and gauges, as well as the Helm Master EX joystick control system for one or more engines.

"The all-new 4.3-litre V6 Offshore F350 merges all the best tech from our full line of outboards with some impressive tech of its own," Yamaha said.

"The result is a perfectly balanced, deep-breathing V6 that delivers jaw-dropping power and the best power-to-weight in its class—the new, 4.3L V6 Offshore F350."

Yamaha Australia said a handful of the new F350s should be in Australia in time for this year's Sanctuary Cove International Boat Show, with plans to fit two boats with test engines and have another on display off the water.

Arrival time for customers? After it launches on the North American market we could expect the new BF350 to go on sale in time for owners to have them fitted and ready to hit the water ahead of next summer.

The new engine differs from the 300hp Yamaha F300 in that while it uses the same 96mm cylinder bore, the stroke increases by 2.0mm to 98mm to make the F350 an undersquare engine that helps it produce more low-end torque.

The engine uses variable camshaft timing to boost power and throttle response in the low- and mid-rev range. Oil capacity is also increased, up from 6.3 litres in the F300 to 7.9 litres in the F350.

While the 300hp of the F300 is produced at 5500rpm, the F350 produces its peak performance at 6000rpm, the maximum end of the rev range, meaning prop selection is likely to be important to squeeze out the new engine’s best performance. The 1.75:1 gearbox ratio is much lower than the other 350hp engines on the market, too, hinting at the amount of torque this engine is capable of producing.

Also new to this engine is the ability to divert the engine’s exhaust away from the propeller while in reverse gear and above 2500rpm, improving the propeller’s ability to bite the water and back up on a fish.

Yamaha has supplied official performance data on a single-engine installation, although for an 8.5-metre Bennington 25QSBA weighing around 2300kg and running a 15.5-inch by 17.0-inch Saltwater Series II stainless steel propeller – pontoon boats are one of the most popular styles sold in the US.

According to the figures, the Bennington hit 22.5 knots at 3500rpm, burning 31.4 litres an hour. At 4500rpm, the speed lifted to 30.9 knots and 53.0 litres an hour, and at WOT 43.1 knots and 118 litres an hour.

The new engine is available in pearlescent white, traditional Yamaha grey or a new colour called classic white – there's no black on offer.

One of the big changes with this new engine is a new dog clutch. Compared with the one used on the F300, the one used on the F350 has more teeth machined into it to handle the extra torque that the more powerful engine produces.

The engine also has a new cowling exhaust port and a strator fan that provides more engine cooling and charging performance, especially lower down in the rev range where heat soak becomes significant.

The Yamaha F350 should be a popular engine for offshore boats from around 7.0 metres in length, and for the growing number of even larger boats fitting multiple engines on the transom to provide the performance they need.