The MerCruiser 3.0 L engine comes equipped with an alternator belt that operates the alternator. As the belt is traveling around the alternator pulley, it enables the alternator to be able to send the proper amount of voltage to the battery. The belt is a V-belt that is seated deep inside of the alternator pulley. This design makes it easier for the belt to be able to turn the alternator pulley. Over time, the belt will fray and crack. Once this happens, change the belt out as soon as possible or the belt could break.
Locate the adjustable slide bracket on the front of the alternator. Loosen the lock nut in the center of the slide bracket with a ratchet and a socket.
Loosen the alternator mounting bolt that secures the top part of the alternator to the 3.0 liter engine with the ratchet and socket.
Push the alternator toward the center of the engine to loosen the tension from the belt. Slide the belt out of the alternator pulley and the other accessory pulleys.
Slide the new belt around the alternator pulley and the other accessory pulleys. Slide the pry bar between the alternator and the alternator bracket. Pry the alternator until the belt is tight. Once the belt is tight, tighten the lock nut in the center of the slide bracket with the ratchet and socket.
Check the tension of the belt by pushing downward on the belt with your hand. The belt should have no more than a half-inch of free play. If so, loosen the lock nut and adjust accordingly.
Tighten the alternator mounting bolt with the ratchet and socket. Remove the pry bar from behind the alternator.
Crank the 3.0 liter engine for about ten seconds and then shut the engine off. Recheck the tension of the belt and adjust if necessary.
