Yamaha’s biggest, most powerful offering to date ups the technological ante.

Beast of the Far East

Yamaha’s most powerful offering debuts a number of new features and some industry firsts.

Yamaha 425-hp XTO Offshore - Profile

Yamaha 425-hp XTO Offshore - Profile

Way back in 2007, when we used our cellphones to actually speak to one another (texting “hello” meant striking 13 keys on our phones’ T9 keyboards), Suzuki fired a shot across the bow of the Big Three—Evinrude, Mercury and Yamaha—as the first outboard manufacturer to have a 300-hp engine in its arsenal. The horsepower war was on. 

Each manufacturer followed suit with models of 300-hp and up. Boatbuilders took note, expanding the LOA of current models and developing new outboard-powered lines. This trend continues to dominate the industry: At last year’s Ft. Lauderdale boat show there were over 560 boats exhibited with outboards. And the fever for these engines at February’s Miami show was stronger than ever, with two 50-plus-foot models flaunting hex (that’s six) high-horsepower engines on their transoms.

Something else I noticed in Miami was the big uptick in vessels sporting Yamaha’s latest offering—the behemoth, 5.6L, 425-hp XTO Offshore. New to the market last year, they seemed to be everywhere in multiple configurations of up to five powerplants.

Quad 425-hp Yamaha XTOs pushed the SeaHunter 45 to a top speed of 60 knots.

Quad 425-hp Yamaha XTOs pushed the SeaHunter 45 to a top speed of 60 knots.

For a company known for both innovation and reliability, it wasn’t enough for Yamaha to hold the horsepower high-water mark among the legacy brands; they used the introduction of their largest powerplant to showcase a number of technological advances. I joined Yamaha’s Outboard Engines Product Manager Ry Landry and OEM Applications Manager Chris Holbrook on board a quad 425-hp- equipped SeaHunter 45 in South Florida to learn more.

I immediately admired how clean the installation looked with just a rigging tube and no hydraulic lines or other electrical harnesses jutting out of the engine and into the splashwell. Holbrook motioned to a cylinder shape above the mounting bracket, pointing out the first-ever electrical power steering system—one of a handful of the 425’s industry firsts. “[The 425] responds instantly with electric steering signals sent directly from the helm to the integral steering control unit. Without hydraulic lines, the steer-by-wire system makes for a cleaner, smoother and easier install,” he said.

Landry expounded on the engine’s other advantage: power savings. “The power steering only draws when in active use, [giving] more amperage to use elsewhere,” he explained, adding, “the [XTO] is rated at 90 peak amps, with 58 amps net at idle and 72 amps net at 1500 rpm.” Translated, that means the engines won’t dominate power usage at trolling speeds, obviating a need to run a genset to keep batteries topped off. With the amount of electronics on board today’s vessels, this is a welcome feature.

The heavy traffic on Ft. Lauderdale’s Stranahan River gave us time to delve into more of the XTOs systems, including direct fuel injection, another industry first for a four-stroke. Combined with a sportscar-like 12.2:1 compression ratio, the three-stage system sprays fuel up to 2900 psi directly into the combustion chamber. This will help maximize the power of 425 horses in not just speed but fuel efficiency. “We are seeing significantly better fuel burns than on the [Yamaha] F350 with 10 percent better [efficiency] at the top end,” Landry said.

Yamaha 425-hp XTO Offshore

Yamaha 425-hp XTO Offshore

The Achilles’ heel of all of this power is delivering it to the water efficiently, so Yamaha paired the 425 with its largest available propeller: up to 17 1/8 inches. In reverse, the exhaust is diverted away from the prop at engine speeds below 2500 rpm for pinpoint control during close-quarters maneuvering or when backing down on big gamefish. According to Holbrook, the “big props can handle the torque and greater thrust” that the 425 will produce (Yamaha does not publish torque ratings), with up to 300 percent more reverse thrust than the F350, Yamaha’s next-largest engine.

As we neared Port Everglades Inlet and traffic started to clear, SeaHunter’s Capt. Bernie Perez pushed the throttles forward and the 27,000-pound boat blasted off. The acceleration at the lower end of the rpm range was impressive: The 45 jumped from 13 knots at 1800 rpm to 43 knots at 4300 rpm in a blink, with a combined fuel burn of 0.59 mpg. At 5200 rpm, she maintained an average speed of just over 51 knots on the way to a WOT of 60 knots. Throughout the range the vessel handled beautifully with an instantaneous, high-performance-like response at the helm, a credit to the combined systems.

Yamaha sees the XTOs not just as raw power to move big, heavy boats but as a fully integrated boat control system to be used in multiple configurations. Working in concert with Yamaha’s Helm Master joystick controls that include three specific modes—one to keep heading, one to keep position and a mode that combines both features, all of which are easily tweaked via joystick—as well as slow trolling at less than idle speed gives the user a wealth of control options while angling, waiting for a bridge to open or a spot to clear at their favorite dock bar.

Yamaha 425-hp XTO Offshore - Rear view

Yamaha 425-hp XTO Offshore - Rear view

These are not small engines: Compared to the 695-pound, 30-inch- shaft Merc 400Rs, the XTO tips the scales at 977 pounds. However, the builders and captains I spoke to all seemed to agree that the weight of these powerplants have already been considered. Yamaha designers maintained a 28 1/2-inch mounting center that’s common on its smaller engines for an easier repower. Regarding the still popular 300- and 350-hp models, Landry said that “The suite of features will trickle down to the F350 and others in the model line.”

One thing I kept hearing on the docks is that today’s powerful outboards allow builders to put so much more in a boat. Yamaha’s XTO now stands at the top of the heap for horsepower ratings among legacy brands. I’d expect them to be challenged sometime soon. In addition, the industry’s most powerful outboard engines—made by Seven Marine—made good on their merger with Volvo Penta with an integration package that merges the best of both companies (see “The Shape of Boating to Come” on page 32). One thing is for certain: As engines and vessels continue to grow in power and size, we all benefit.

This article originally appeared in Outboard magazine.

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