Mercury Marine MCM 3.0L — Maintaining Closed Cooling Coolant Level
Maintenance · Cooling System
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
- Allow engine to cool down before removing pressure cap; sudden loss of pressure could cause hot coolant to discharge violently
Procedure
- Allow engine to cool before removing pressure cap.
- Turn cap 1/4 turn to allow pressure to escape slowly, then push down and turn off.
- Coolant level in heat exchanger should be full (to bottom of filler neck).
- Coolant level should be between ADD and FULL marks on coolant recovery reservoir with engine at normal operating temperature.
- Reinstall pressure cap until it contacts stop on filler neck.
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.