MerCruiser GM4 Service Manual page 33

6. Insert a small wire (repeatedly) to make sure that
vent holes and water drain holes and passages
(as shown) are unobstructed and open.
d
a
a - Speedometer Pitot Tube
b - Trim Tab Cavity Vent Hole
c - Trim Tab Cavity Drain Passage
d - Gear Housing Water Drain Hole
(One Each - Port and Starboard)
e - Gear Housing Cavity Vent Hole
f - Gear Housing Cavity Drain Hole
7. Crank engine over SLIGHTLY, with starter motor,
to purge any water trapped in seawater pickup
pump. DO NOT ALLOW ENGINE TO START.
! CAUTION
If boat is in the water or is to remain in the water,
seacock (if so equipped) must remain closed un-
til engine is to be restarted, to prevent water from
flowing back into cooling system. If boat is not
fitted with a seacock, seawater inlet hose must re-
main disconnected and plugged, to prevent water
from flowing into cooling system and/or boat. As
a precautionary measure, attach a tag to the igni-
tion switch or steering wheel with the warning
that the seacock must be opened or the seawater
inlet hose reconnected prior to starting the en-
gine.
Index
90-816462 2-695
e
b
f
c
71216
f
c
70134
8. After cooling system has been drained complete-
ly, coat threads of drain plugs with Quicksilver
Perfect Seal and reinstall. Tighten drain plugs se-
curely. Reconnect hoses and tighten all hose
clamps securely. If NOT equipped with sea-
cock: seawater inlet hose must remain discon-
nected and plugged until engine is to be restarted.
IMPORTANT: MerCruiser recommends that pro-
pylene glycol antifreeze (nontoxic and biode-
gradable, which makes it friendly to lakes and riv-
ers) be used in sea-water section of the cooling
system for cold weather or extended storage.
Make sure that the propylene glycol antifreeze
contains a rust inhibitor and is recommended for
use in marine engines. Be certain to follow the
propylene glycol manufacturer's recommenda-
tions.
9. For additional assurance against freezing and
rust, remove the thermostat cover and thermo-
stat. Fill the engine seawater cooling system with
a mixture of antifreeze and tap water mixed to
manufacturer's recommendation to protect en-
gine to the lowest temperature to which it will be
exposed during cold weather or extended stor-
age. Using a new gasket, reinstall thermostat and
cover. Tighten cover bolts to 30 lb. ft. (41 N·m).
a
b
c
d
a - Lifting Eye
b - Cover
c - Gasket
d - Thermostat
e - Hose
f - Fitting
g - Housing
NOTE: Hoses shown removed only to indicate flow.
Do not remove hoses.
e
f
g
72589
MAINTENANCE - 1B - 17