The compression ratio is increased to 10:1 from 9.7:1, but a more sophisticated knock sensor allows the new motor to run well on 87-octane fuel. The double-overhead cam cylinder head has larger-diameter intake and exhaust valves that boost mid-range torque, and flow through the engine is further enhanced by a new 60mm throttle body, revised intake with a tuned resonator, and a new exhaust design. Displacement is increased to 1832cc from 1741cc. While not a radical redesign, the new F115B offers improvements from top to bottom. Except for minor updates in 2011, which we showed you in the video Sneak Peek at the New Yamaha F115, this engine was unchanged since its debut in 1999. In designing the F115, Yamaha used new engine design and casting techniques developed for its ground-breaking line of off-road motorcycles, which started a four-stroke revolution in that market. The F115 was still a bit heavier than a two-stroke, but its fuel economy, reliability, and quiet operation were advantages that off-set any weight penalty. The original Yamaha F115A recalibrated our expectations for four-stroke outboards when it was introduced in 1999, proving that the weight and size of a four-stroke outboard could be paired down to compete with two-stroke motors. The new Yamaha F115 four-stroke outboard should be ideal for powering small runabouts and fishing boats.