Mercury 305 CID, Service Manual, Page: 800 / 967

6B-26 - CLOSED COOLING MODELS 90-823225--1 1096
74745
a
c
b
f
g
d
e
Models With Serpentine Belt
a - Thermostat Housing
b - Thermostat
c - Quad-Ring Seal
d - Screws with Lockwashers
e - Thermostat Cover
f - Gasket
g - Bleeder Valve
6. Connect hoses to thermostat cover. Tighten hose
clamps securely.
! CAUTION
Avoid seawater pickup pump impeller damage.
DO NOT operate engine without cooling water
being supplied to seawater pickup pump.
7. With boat in the water and/or cooling water prop-
erly supplied to seawater pickup pump, start en-
gine and inspect for leaks.
Changing Coolant
NOTICE
For information and procedures on draining
the seawater cooling system, refer to SEC-
TION 6A. For cold weather or extended stor-
age, refer to SECTION 1B.
Closed Cooling Section
Closed cooling section of closed cooling system
should be kept filled year-round with recommended
coolant solution. Do not drain closed cooling section
for storage, as this will promote rusting of internal
surfaces. If engine will be exposed to freezing
temperatures, make sure that closed cooling section
is filled with an ethylene glycol antifreeze and water
solution, mixed to manufacturer’s recommended
proportions, to protect engine to lowest temperature
to which it will be exposed. If necessary, change
coolant.
Coolant Recommendations
! CAUTION
Alcohol or Methanol base antifreeze or plain
water are not recommended for use in fresh
water section of closed cooling system at any
time.
It is recommended that the coolant section of closed
cooling system be filled with 50/50 mixture of ethy-
lene glycol antifreeze and water. In areas where the
possibility of freezing DOES NOT exist, it is permissi-
ble to use solution of rust inhibitor and water (mixed
to manufacturer’s recommendations).
Change Intervals
Drain and flush coolant from the closed cooling
system at least every two years or whenever exhaust
gases have entered the system.