Mercury Marine MCM 4.3L / MCM 4.3L EFI — Flushing Seawater Cooling System
Maintenance
For the Mercury Marine MCM 4.3L / MCM 4.3L EFI, from the Mercury Marine service manual.
Before you start
- Ensure area around propeller is clear; remove propeller to avoid injury
- Watch temperature gauge to ensure engine does not overheat
Procedure
- Install flushing attachment and water hose over water pickup holes in gear housing.
- Open water tap about 1/2 of maximum capacity.
- With drive in neutral, start engine and advance throttle to 1300 rpm.
- DO NOT run engine at idle; do not exceed 1500 rpm.
- Run engine for 10 minutes or until discharge water is clear.
- Slowly return throttle to idle and turn engine off.
Tools required
- Flushing attachment and water hose Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Run engine at 1300 rpm
- Do not exceed 1500 rpm
- Run 10 minutes
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.