America's Definitive Marine Engine Magazine
There are plenty of outboard re-powers and other applications where drive-by-wire technology is not appropriate. Enter the newly reintroduced mechanical Yamaha outboard F250. This particular model outboard motor is only compatible with cable control boxes. That said F200/F250 communicates with Yamaha's Command Link electronic gauges via a gateway and also communicates with NMEA-2000 compatible displays.
Regardless of the shift interface, the Yamaha F250 powerhead is well-endowed with stat of the art technology. The build list includes Variable Camshaft Timing, technology that allows the Engine Control Module to advance or retard camshaft timing based on the engine rpm. Doing so increases efficiency in the low- and mid-rpm ranges. In other words there's more torque in the 2,000 to 3,500 rpm range, where outboards do most of their challenging work.
Yamaha outboards F250 draws its breath through a single throttle valve that meters airflow through long tube intake tracks. Long tube intake tracks have long been renowned for the way they pump up to low-end and mid-range torque. I first saw it back in the 60's on the venerable Chrysler slant six car engine. For Yamaha Motor's engineers to incorporate long track intake runners in a 4-stroke outboard more was an eminently wise choice.
There's more eminently good news. The knock sensor integrated into the ECM protects the piston domes and crankshaft journals against low octane gasoline at the same time it maxes all available horsepower. Because the engine knows exactly where the danger zone is for ignition advance, it can safely bump up horsepower right up against the danger mark. The payoff is maximum acceleration without eroding fuel economy.
With this engine the story is not only about the raw, bloody horsepower. For example the flywheel has been fitted with rubber dampener that dramatically reduces vibration. And Yamaha's Shift Dampener System propellers are available for both the F250 outboards.
The F250 V-6 outboard is protected by Yamaha's 3-year limited warranty for pleasure use and a 1-year limited commercial warranty term. And finally, Yamaha's closed fuel vapor system and other hardware helped the F250 earn this engine a three-star rating for ultra-low emissions from the stringent California Air Resources Board. In addition, the outboard meets or exceeds all Federal emissions requirements.
|Cylinder head||DOHC - 24 Valves|
|Operating Range||5000-6000 rpm|
|Compression Ratio||9.9 to 1|
|Fuel||Minimum 89 Octane|
|Gear ratio||2.00 to 1|