A company like Yamaha doesn’t develop a 350-hp outboard on a whim. Years are committed to the project, myriad ideas are considered, money is invested, and of course, there must be consumer demand.
The 4.3-liter F350 was introduced in mid-January and will be available for consumers this spring. “There were enough people for whom the XTO and the 300 weren’t the right fit,” said Lucy Berg, senior product specialist at Yamaha U.S. Marine Business Unit. “When enough of our customers say, ‘We need something from you,’ we’re going to react.”
Yamaha previously built a 350-hp outboard based on a 5.3-liter powerhead. That engine was discontinued in 2020. The company introduced the 4.2-liter 300 in 2009 and the 425-hp XTO Offshore in 2018.
David Meeler, technical marketing manager at Yamaha, said that when it comes to engine development, “we’re going to draw out all the alternatives and go with what makes the most sense. It’s the willingness to spread out all the technological advances we’ve had since the 4.2 came out. We took all the technology and melded it together.” The previous F350 had flywheel issues that hampered reliability, so when it was discontinued, there was a pretty big power gap in the company’s high-horsepower outboard lineup.
Meeler said that the new F350 was in development for about three years, and that three to four years is the typical time frame for Yamaha to bring to market a new outboard in this size range. The plan was to work off the 4.2-liter powerhead used for the F300.
“The 4.2-liter [powerhead] has a proven track record of reliability,” Berg said. “We had a responsibility to fill our horsepower gaps and pay attention to the biggest ask, which was to keep it lightweight.”
An F350 in a 25-inch shaft length weighs 629 pounds, which Meeler said makes it the lightest outboard in this power rating. It’s only 18 pounds heavier than the F300.
By comparison, Mercury’s V-10 350 Verado has a 5.7-liter displacement, and the dry weight of the lightest model is 695 pounds. Suzuki’s DF350A has a 4.39-liter V-6 powerhead, and the 25-inch version tips the scales at 727 pounds. Honda’s first V-8 outboard, the BF350, has a 4.95-liter powerhead. With a 25-inch shaft length, it weighs 765 pounds.
Because engines in this size range can be installed in quad and quint applications, the width of the outboard becomes an important dimension. The new F350 mounts on 28.5-inch centers. This number is similar to Mercury’s specifications, while the Suzuki DF350 installs on 26-inch centers.
While some people would expect that the F350s are targeted for bigger offshore center consoles, Meeler said the outboard will work in myriad applications. He was at the Minneapolis Boat Show in January and envisioned the engine working on larger walleye and multispecies aluminum boats, as well as pontoons.
“The F350 is perfect for all those applications,” he said . “You’ll see this motor up and down the coast, inland and offshore.”
Though the F350 is built on the same block as the F300, it has an extra liter of displacement thanks to a longer stroke created by a newly designed crankshaft. Plasma-fused cylinders have a micro-textured surface, helping to increase displacement and deliver better performance. Total displacement for the F350 is 4.3 liters, and the compression ratio is 11-to-1. The naturally aspirated F350 runs on 89-octane gasoline.
Yamaha also borrowed from the XTO Offshore, which is rated at 425 and 450 hp. The F350 uses the same 81mm diameter electronic throttle valve as the XTO, and larger intake and exhaust valves than on the F300. The intake manifolds on the F350 have 40% larger surge tanks to maximize the amount and timing of air entering the intake ports.
An improved camshaft profile establishes higher valve lift for longer opening duration during intake and exhaust, and there are new lifters made from the same material as those used in the XTO 450. The F350 has Iridium spark plugs, and Yamaha developed new fuel injection control mapping to create a longer injector duration.
For durability, the F350 incorporates the same water sensor for overheat control from the XTO, to catch increasing engine temperatures sooner. An intake silencer provides a sound buffer so the engine produces less operating noise. The oil cooler on the F350 is larger than on the F300.
To distribute the extra power to the water, the F350’s lower unit has a new dog clutch machined with more teeth to better handle the extra torque. The gearcase also has Yamaha’s Thrust Enhancing Reverse Exhaust technology that keeps exhaust bubbles above the anti-ventilation plate and away from the propeller at 2,500 rpm when in reverse. This setup produces higher thrust when backing down on a fish or maneuvering around a dock or other fixed object.
The F350 is offered in full model 25- or 30-inch shaft lengths, and in 25-, 30- and 35-inch versions for late-stage customized lower unit models. The latter are equipped with an intermediate drive shaft and shift rod.
Berg said her favorite innovation is in the F350’s charging system. A stator fan like the one on the XTO pulls heat away from the stator and sends it out of the cowling via an exhaust port.
“We have better performance for net charging across all rpms, but especially at lower rpm,” she said . The alternator is rated at 70 amps, but where it makes noticeably more power is at idle, 31.7 amps, and at trolling speeds, 15 amps. Yamaha said this is three times the output produced by the F300 at those speeds.
For smoother operation, the F350 has Yamaha’s Digital Electric Steering and the Helm Master EX control system, with navigation and fishing features including autopilot, SetPoint, joystick integrated bow thruster control, lock-to-lock steering settings and operator-tailored helm friction settings.
There’s also a connection port on the rigging tube for an automatic flushing system. Manual flush is possible with a separate connection. TotalTilt technology, used on all Yamaha outboards with Helm Master EX, is on the F350. A double tap of the “up” or “down” button will move the outboard through its tilt and trim range, automatically stopping at the preset limit at the top of the range or upon trim ram contact at the bottom.
Also part of the Helm Master EX package is an optional propeller light rear panel on the outboard cowling. It flashes when Full Maneuverability SetPoint Features engage the propeller.
The engine is available in pearlescent white, traditional gray and classic white.
Retail pricing starts at $40,000 for the 25-inch stock shaft model. The 25-inch F300 in a DEC-only model costs about $5,000 less, while the XTO 425 starts at $49,000. The F350 is expected to be available for the 2024 boating season, with the potential for more new products to come.
“We’re always looking to advance and further our product,” Berg said . “If our customers ask for something, we’ll always look at it.”
