Yahama has a new version of the F115 four-stroke outboard, and we got a sneak peek at it on Monroe Reservoir, in Indiana. Then we sat down with a Yamaha tech, he talked through what's different about this engine, and we took a test drive on an Alumacraft Dominator 175 CS.
There are two main advancements in the F115. First, they switched to a single throttle body fuel injection system. This improved economy, and reduced maintenance. Second, they added a knock sensor. This helps protect the engine against knocking caused by low octane fuel. In other words, it's a calculated effort to eliminate some of the problems associated with aging ethanol-laced fuel, by retarding the timing.
When we took the Alumacraft off the dock and nailed the throttle, the F115 (with a 13" x 19" three-blade aluminum prop swinging through a 2.15:1 gear reduction) popped us up onto plane and ran the 2,453 pound rig up to 30-MPH in just over seven seconds. And in less than 15 seconds, we hit a top-end speed of 42.9-MPH. At a 3500 RPM, 21.5-MPH cruise we burned 3.3 gallons per hour, for 6.5 miles to the gallon. And at wide-open we burned 9.9 gallons per hour, for 4.3 miles to the gallon. Check out the video - you'll see for yourself, it's one sweet ride!