Mercury Marine MCM 3.0L — Valve Adjustment - Engine Not Running

Adjustments · Valve Train

For the Mercury Marine MCM 3.0L, from the Mercury Marine service manual.

Applies to: General Motors MCM 3.0L / 3.0LX engine

Procedure

1. Crank engine until mark on torsional damper lines up with center 0 mark on timing tab, engine in No. 1 firing position.
2. Adjust No. 1 cylinder exhaust and intake, No. 2 intake, No. 3 exhaust, No. 4 intake.
3. Back out adjusting nut until lash is felt at push rod, then turn in until all lash is removed.
4. Tighten adjustment nut an additional 3/4-turn.
5. Crank engine one revolution until pointer 0 and damper mark align (No. 4 firing position).
6. Adjust No. 2 exhaust, No. 3 intake, No. 4 exhaust.
7. Install distributor cap, spark plug wires and coil lead.
8. Install rocker arm cover; torque to 40 lb. in. (4.5 N-m).

Source: Mercury Marine service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

More Mercury Marine repair guides →