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Overview: Yamaha XTO 425 V8 Offshore Outboard

Yamaha V8 Outboard  on a Grady White boat

World's First
Direct Injected 4-Stroke Outboard

Simply put Yamaha Marine's XTO Offshore is a 425-horsepower, naturally-aspirated, big block V-8 (5.6L) outboard designed to power heavy offshore boats whose Jovian size requires a large diameter propellers swinging from a robust gear case.

Phantom drawing of Yamaha XTO Direct-Injection

While this Yamaha Marine offering is undoubtedly big and powerful, that's not necessarily the big news. But what is news is its Direct Injection, qualifying it as the first four-stroke outboard ever to take advantage of this technology. Previously only two-stroke outboards enjoyed this technology. For those who may be unfamiliar with DI, it sprays high pressure fuel (as much as 2900 PSI) directly into the combustion chamber, rather than the intake track, just before the intake valve. That pays huge dividends in throttle response. There's no waiting for additional fuel to make its way from a conventionality injector, down the air intake, past the intake valve and finally into the combustion chamber It is in a word, instantaneous.

Phantom drawing of Yamaha 425 hp V8-Powerhead

Beyond DI, techies will go wild upon learn the particulars of the reciprocating mass and its component parts. Deep inside the valley of the V-block reside carbon-coated shim-less, bucket-type valve lifters renowned for the way increase durability. Similarly, a dual-chamber oil pump oil flow a massive volume of lubricant to to lube and cool Crankshaft journals and piston skirts. Gone are conventional cylinder liners, mere steel replaced by plasma fused liners replete with micro-textured surface that engineers boast is 60-percent harder than steel, and significantly lighter. Their micro-fine/smooth surface reduces piston drag which in turn increases fuel economy. The cooling system features a bank of four thermostats, two thermostats per cylinder bank, a scenario that improves coolant flow and better regulates of engine and oil temperature. The 12.2 to one compression ratio new engine is the highest for any outboard motor extant. You already know higher compression ratio squeeze more horsepower out of every drop of fuel. So throttle response is stronger. A complement of Iridium-tipped spark plugs fire a hotter spark, also improving throttle response, peaking power and extend ed the time between plug changes, saving money on parts and labor. For perspective, in cars Iridium plugs are known as 100,00 mile spark plugs.

As for the topic of maintenance, V8 XTO Offshore's innovative gear case lubricant exchange system allows draining and refilling gear case oil while the boat is still floating in the water. Three different shaft lengths are available: 25-inches, 30-inches and 35-inches.

Yamaha marine's V8 XTO Offshore steering system is not burdened by hydraulic lines or linkages. Instead, steering is fully electric. Rigging is as easy as plugging in a harness. In operation, the steering control unit receives electrical signals from a cylinder position sensor to carry out joystick and steering commands.

A novel exhaust-gas relief system produces reverse thrust up to 300-percent more than previous incarnations, effectively allowing the exhaust to exit the engine above the propeller when the engine is put into reverse, The payoff of this scenario is that the propeller blades grabs clean water instead of aerated water. Finally, XTO Offshore features a five-year limited warranty for pleasure use.

studio shot of yamaha marine x435 outboard motor
XF425 5.6L V8 Specifications:
Model Code XF425
Color Pearlescent White
Alternator Output Max. Gross - 90 Amps
Cylinders 4 Valves per Cylinder
Engine Type V8
Ignition TCI Microcomputer
Starting Electric with PTT
Exhaust Through Propeller (Except in Reverse Under 2,500 rpm)
Power 425 Horsepower
Displacement 5,600 Cubic Centimeter
Bore x Stroke 96 x 96 mm (3.78 x 3.78 in)
Shaft Length 25"
Dry Weight 952 lbs
Steering Integrated, Electric Actuation
Fuel Type Unleaded
Use Fresh and Salt Water
Full Throttle RPM Range 5,000 - 6,000 rpm
Fuel Induction Direct Injection / Up to 2900 PSI
Recommended oil Yamalube® 4M
Oil capacity 7.8 / 7.5 l
Cooling Thermostatic control
Gear Ratio 1.79 to 1
Gear Shift Forward, neutral, reverse
Trim Range -4° through +16°
Degree of tilt - -4° through +73°
Propeller Counter-rotating
Additional Colors Yamaha Gray
Pearlescent White
Warranty term Limited 5-Year Pleasure, 3-Year Government, 1-Year Commercial