Flushing Seawater Section Of Closed Cooling System - MerCruiser GM4 Service Manual

! CAUTION
Avoid seawater pickup pump impeller damage.
DO NOT operate engine without water being
supplied to seawater pickup pump.
5. With boat in the water and/or cooling water prop-
erly supplied to seawater pickup pump, start en-
gine and inspect for leaks.
Flushing Seawater Section of
Closed Cooling System
If engine is operated in salty, polluted or mineral-lad-
en waters, seawater section of closed cooling system
should be flushed periodically (preferably after each
use) with fresh water to reduce corrosion and prevent
the accumulation of deposits in the system. Seawater
section also should be thoroughly flushed prior to
storage.
! WARNING
When flushing cooling system with boat out of
the water, be certain that area in vicinity of propel-
ler is clear and that no person is standing nearby.
As a precautionary measure, it is recommended
that propeller be removed.
! CAUTION
Do not run engine above 1500 RPM when flush-
ing. Suction created by seawater pickup pump
may collapse flushing hose, causing engine to
overheat.
! CAUTION
If cooling system is to be flushed with boat in the
water, seacock (if so equipped) must be closed,
or water inlet hose must be disconnected and
plugged to prevent water from flowing into boat.
! CAUTION
To prevent engine or stern drive unit damage DO
NOT run engine or drive unit without water being
supplied to water intake openings on gear hous-
ing.
! CAUTION
Watch temperature gauge at dash to ensure the
engine does not overheat.
Index
90-816462 2-695
1. Connect flushing attachment as follows:
NOTE: If flushing cooling system with boat in water,
raise drive unit to trailer position, install flushing at-
tachment and lower drive unit to full IN/DOWN posi-
tion.
a. Install Quicksilver Flushing Attachment (or
equivalent) over water intake openings in
gear housing.
b. Connect hose between flushing attachment
and water tap.
a - Quicksilver Flushing Attachment
b - Garden Hose
! CAUTION
If cooling system is to be flushed with boat in the
water, seacock (if so equipped) must be closed,
or water inlet hose must be disconnected and
plugged to prevent water from flowing into boat.
c. Close seacock (if so equipped) or disconnect
and plug seawater inlet hose.
2. Partially open water tap (approximately 1/2 maxi-
mum capacity) and allow drive unit and cooling
system to fill completely. Do not use full tap water
pressure.
NOTE: Drive unit is full when water is discharged out
of drive unit, and/or seawater section of closed cooled
system is full when water is discharged through pro-
peller.
3. Place remote control lever in NEUTRAL position
and start the engine. Operate engine at idle
speed in NEUTRAL gear for 10 minutes or until
discharge water is clear, then stop engine.
CLOSED COOLED MODELS - 6B - 11
a
b
72672