To adjust the throttle cable on a boat, put the motor in neutral, examine the cable, disconnect the throttle cable from the shifter, adjust the cable and reattach it. Some makes and models of boat motors may have different methods of adjusting the throttle cable tension.
Look for sharp bends, slack loops or kinks when inspecting the throttle cable, and remove or straighten out anything that you find. Adjust the tensioning nut around the throttle cable that is usually located where the cable is attached to the engine's throttle body. Test the adjusted tension by reattaching the cable to the shifter and moving it into the full forward position. Make additional adjustments as necessary.