America's Definitive Marine Engine Magazine
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.
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.
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.
|XF425 5.6L V8||Specifications:|
|Alternator Output||Max. Gross - 90 Amps|
|Cylinders||4 Valves per Cylinder|
|Starting||Electric with PTT|
|Exhaust||Through Propeller (Except in Reverse Under 2,500 rpm)|
|Displacement||5,600 Cubic Centimeter|
|Bore x Stroke||96 x 96 mm (3.78 x 3.78 in)|
|Dry Weight||952 lbs|
|Steering||Integrated, Electric Actuation|
|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|
|Gear Ratio||1.79 to 1|
|Gear Shift||Forward, neutral, reverse|
|Trim Range||-4° through +16°
Degree of tilt - -4° through +73°
|Additional Colors||Yamaha Gray
|Warranty term||Limited 5-Year Pleasure, 3-Year Government, 1-Year Commercial|