Engine Final Alignment - Mercury MerCruiser MCM 454 Mag MPI Service Manual

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MIE MODELS - VELVET DRIVE TRANSMISSION

IMPORTANT: Engine bed must position engine so that a minimum of 1/4 in. (6 mm)

up and down adjustment still exists on all four mounts after performing final

alignment. This is necessary to allow for final engine alignment.

4. Lift engine into boat and position on engine bed so that transmission output flange and

propeller shaft coupler are visibly aligned. No gap should be seen between coupling

faces when butted together. Adjust engine bed height, if necessary, to obtain proper

alignment. DO NOT use mount adjustments to adjust engine position at this time.

5. Check all four mounts to ensure that they are still positioned properly, then fasten

mounts to engine bed with appropriate bolts or lag screws and hardware. Tighten lag

bolts/screws securely.

6. Disconnect and remove sling. Proceed to "Engine Final Alignment" section following.

Engine Final Alignment

To avoid vibration, noise and damage to transmission output shaft oil seal and

bearings, engine must be properly aligned.

IMPORTANT: Engine alignment MUST BE RECHECKED with boat in the water, fuel

tanks filled and with a normal load on board.

Engine must be aligned so that transmission output flange and propeller shaft coupler

centerlines are aligned and coupling faces are parallel within .003 in. (0.07 mm). This

applies to installations with solid couplings, as well as flexible couplings.

1. Check mating surfaces on transmission output flange and propeller shaft coupler faces

to make sure they are clean and flat.

2. Center propeller shaft in shaft log as follows:

a. Push down and lift shaft as far as it will move. Then place shaft in the middle of the

b. Move shaft to port and then to starboard as far as shaft will move. Then place shaft

c. With shaft in center of shaft log, as determined by above procedures "a" and "b,"

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in the middle of the movement.

align engine to shaft.

SERVICE MANUAL NUMBER 23

90-861326--1 MARCH 1999

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