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Home›Repair guides›Mercury Marine›Flushing Cooling System

Mercury Marine MCM 3.0L — Flushing Cooling System

Maintenance

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

  • Do not run engine above 1500 RPM when flushing
  • Be certain area in vicinity of propeller is clear
  • Watch temperature gauge to ensure engine does not overheat

Procedure

  1. Install Quicksilver Flushing Attachment over water intake openings in gear housing.
  2. Connect hose between flushing attachment and water tap.
  3. Partially open water tap (about 1/2 maximum capacity) and allow system to fill completely.
  4. Place remote control lever in NEUTRAL and start engine.
  5. Operate engine at idle in NEUTRAL for 10 minutes or until discharge water is clear, then stop engine.
  6. Shut off water tap.
  7. Remove hose and flushing attachment.

Tools required

Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.

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.

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