Yamaha F115JB Jet Drive Motor. 25-Inch Shaft Equivalent Remote Control Electric Start Power Trim & Tilt Jet Pump Gray. The Yamaha F115JB Jet Drive Motor pairs Yamaha's proven 115-horsepower inline 4-cylinder powerhead with a factory-installed jet drive for exceptional shallow-water performance. With its 25-inch shaft, this model is designed for anglers, hunters, and boaters who demand reliable power in areas where propeller-driven motors can't operate.. The jet drive lower unit lets the F115JB n