Flushing Seawater Cooling System; 454/502 Mag Mpi And 8.2L Mpi - Mercury MerCruiser MCM 454 Mag MPI Service Manual

Table of Contents

SERVICE MANUAL NUMBER 23

Flushing Seawater Cooling System

454/502 Mag MPI and 8.2L MPI Engines (Except Horizon Model)

If engine is operated in salty, polluted or mineral-laden waters, seawater cooling system

should be flushed periodically (preferably after each use) with fresh water to reduce corro-

sion and prevent the accumulation of deposits in the system. Seawater cooling system also

should be thoroughly flushed prior to storage.

When flushing, be certain the area around propeller is clear, and no one is standing

nearby. To avoid possible injury, remove propeller.

Do not run engine above 1500 RPM when flushing. Suction created by seawater

pickup pump may collapse flushing hose, causing engine to overheat.

IMPORTANT: If cooling system is to be flushed with boat in the water, seacock (if

equipped) must be closed, or water inlet hose must be disconnected and plugged to

prevent water from flowing into boat.

Watch temperature gauge at dash to ensure the engine does not overheat.

1. Close seacock (if equipped) or remove and plug seawater inlet hose.

2. Loosen hose clamp and remove seawater inlet hose at location shown. Connect tap

3. Partially open water tap (approx. 1/2 maximum capacity) and allow cooling system to

4. Place the remote control lever in NEUTRAL position and start the engine. Operate

90-861326--1 MARCH 1999

Downloaded from

https://needmanual.com/

water hose to inlet fitting.

Hose To Cooler

Seawater Inlet Hose

fill completely. Cooling system is full when water is discharged through the exhaust. Do

not use full tap water pressure.

engine at idle speed in NEUTRAL gear for 10 minutes or until discharge water is clear,

then stop engine.

SEAWATER COOLED MODELS

Table of Contents