Mercury Marine MCM 3.0L — Valve Adjustment - Engine 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
Before you start
- Preload adjustment must be done slowly to allow lifter to adjust itself, preventing valve contacting piston
Procedure
- Run engine until normal operating temperature, then remove valve cover.
- With engine at idle, back off rocker arm nut until rocker arm starts to clatter.
- Turn nut down slowly until clatter just stops (zero lash).
- Turn nut down 1/4 additional turn and pause 10 seconds until engine runs smoothly.
- Repeat additional 1/4 turns, pausing 10 seconds each, until nut has been turned down 3/4 turn from zero lash.
- Repeat to adjust other valves.
- Install valve covers, torque screws to 40 lb. in. (4.5 N-m).
Specs & values
- 3/4 turn from zero lash
- Rocker arm cover screws: 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.