When watersport engines are running rough, it is time for a Sta-Bil Marine Tune-Up. The easy-to-use additive pours directly into the fuel tank to address issues caused by ethanol-blended fuels or neglected fuel systems. One treatment is enough to restore lost engine performance in any gasoline-powered watercraft like jet skis, speed boats, and PWCs. Try it the next time your engine seems to be running a bit rough, not performing like you remember.