How do I Change a Drive Belt on a UK Mercruiser Engine

The UK Mercruiser engine is a marine engine that comes in sizes ranging from 3.0 to 5.7 and bigger. The front engine accessories on the Mercruiser engine are controlled by a drive belt. When the engine is running, the drive belt is driven around each engine accessory by the crankshaft pulley on the bottom of the engine. Excessive use and heat exposure can cause the belt to weaken. Once the belt weakens, it can fray or crack. Change the belt out at the first sign of any damage to prevent the engine from shutting down.

Instructions

1

Unbolt the cover from the top of the UK Mercruiser engine with a ratchet and a socket. Pull the cover off so that the front of the engine can be accessed.

2

Locate the alternator on the front right hand side of the engine. Loosen the alternator mounting bolts with a ratchet and a socket. The alternator has a slide bracket attached to the top of the alternator that tensions the drive belt.

3

Loosen the bolt in the center of the slide bracket with the ratchet and a socket. Turn the adjustment bolt that is located on the end of the slide bracket counter-clockwise with the ratchet and socket until the belt tension is loose.

4

Pull the belt off of all of the engine accessory pulleys. Place the belt to the side. Slide the new drive belt around the alternator pulley first and then around the water pump pulley, power steering pump pulley and the crankshaft pulley. The belt will only fit in one direction around the engine accessories so there is no need for a routing diagram.

5

Turn the adjustment bolt on the alternator slide bracket clockwise to tighten the belt. Once the belt is tight, push in on the belt with your hand. The belt should have no more than a half-inch of free play. If so, continue to tighten the belt until there is only about a half-inch of free play in the belt. Tighten the bolt in the center of the slide bracket down tight with the ratchet and socket. Tighten the alternator mounting bolts down tight with the ratchet and socket.

6

Crank the UK Mercruiser engine for about fifteen seconds and then shut the engine back off. Recheck the tension of the belt. Adjust the tension if needed and reinstall the cover over the engine.