This has been a long time coming!
It’s been nearly six years now since the launch of the new XTO series of outboard engines from Yamaha. These brawny V8 engines displace 5.6 liters and boast several new advances in outboard technology (at the time), plus improved reliability. Their 425 hp variant quickly became the class leader in V8 power, allowing Yamaha to sunset the F350 V8 in 2019. Since this time, the XTO’s claim to reliability has been proven, and a new 450-hp model has been released. However, something was still missing from the lineup, and boaters desired more.
The gap between the Yamaha F300 V6 and the new XTO 425 V8 is more than just a couple of cylinders. For example: The V8 power output is a staggering 42% more than the V6. But this huge power comes with a weight penalty: nearly 400 pounds. Boat manufacturers easily overcome these concerns in their design and engineering departments. However, owners who wish to repower are faced with questioning whether or not the existing transom or bracket of their boat can handle an outboard engine weighing north of 950 pounds. Furthermore, there’s a discussion of power-to-weight ratio, prop sizes and pitch, and so much more.
Rest assured, Yamaha engineers were never sitting on their hands or cupping them over their ears; They are always listening to their customers, dealers and builder partners. They also believe in releasing a superior product with new advancements that has endured rigorous real-world testing for thousands of hours. After all, that has been the secret to the XTO’s intense success. “Boaters asked for it, and we delivered,” said Ben Speciale, President of Yamaha’s U.S. Marine Business Unit. “The F350 is the perfect big power, lightweight option for a wide variety of applications.”
Minor Tweaks, Big Gains
This all-new V6 only displaces an additional 87 cc (5.5 cu. in.) over the long-standing F300 V6. Mainly because it is using the same engine block. The displacement increase comes via a different crankshaft that extends each cylinder’s stroke. While this does increase the torque output and helps to lengthen the torque curve, the 50 hp bump in output is all in the top end along with air and fuel management.
The cylinder head houses larger intake and exhaust valves while bumping the compression ratio up to 11:1. These valves are pushed by new high-lift camshafts that offer a longer opening duration. The intake manifolds boast larger surge tanks and are mated at the center with a large 81 mm throttle valve (borrowed from the high-output XTO 450). The extra air input benefits from Yamaha’s new fuel injection control mapping, which increases each injector’s spray duration over the 4.2 liter V6.
Remember that discussion of weight differences between Yamaha’s current V6 and V8 engines? The new 350 hp V6 weighs 629 pounds – a modest 12% increase over the current 300 hp model. Compare that to a 17% increase in output and it’s easy to validate Yamaha’s claims of a class-leading power-to-weight ratio. Plus, all that extra power is obtained when running 89-octane fuel – no high-octane fuel is required!
Hit the Water this Summer with New Power!
The all-new 350 hp V6 engine will be offered in the typical 25″, 30″, and 35″ shaft lengths and in 3 different factory color options including the new Classic White. A great safety feature included with this new V6 is the addition of a flashing light on the back of the motor to show propeller engagement to anyone behind the vessel. This will hopefully trickle down to the other models in Yamaha’s lineup. The official release date of this new engine is Spring of 2024 so we encourage you to connect with the Legasea Marine sales team now to plan your next new boat purchase or repower!
- Engine: 4.3L V6 rated at 350 hp
- Weight: 629 lbs – 653 lbs
- Bore x Stroke: 96 x 98mm (3.78 x 3.86 in)
- Max. Alternator Output: 70 amps
- Compression Ratio: 11.0:1
- Recommended Fuel: Octane 89
- Engine Oil Capacity: 7.9 L (8.4 qt)
- Gear Ratio: 1.75:1
- Shaft Length: 25″ – 30″ – 35″
- Mounting Centers: 28.5″
- Max. Steering Angle; 32° from center, left and right