Filling Closed Cooling Section - MerCruiser 305 CID (5.0L) Service Manual

CLOSED COOLED MODELS

Filling Closed Cooling Section

Alcohol or Methanol base antifreeze or plain water are not recommended for use in
coolant section of Closed Cooling System at any time.
It is recommended that coolant section of Closed Cooling System be filled with a 50/50 mix-
ture of Extended Life Coolant and pure, soft water. This coolant MUST BE used regardless
of whether freezing temperatures are expected to provide adequate corrosion protection.
In areas where Extended Life Coolant is not available and the possibility of freezing DOES
NOT exist, it is permissible to use a solution of rust inhibitor and pure, soft water (mixed to
manufacturer's recommendations).
NOTE: Coolant section capacity is approximately 18 U.S. Quarts (17 L).
1. Fill coolant section of Closed Cooling System with coolant mixture as follows:
a. Open bleeder valve on thermostat housing.
b. Fill with coolant mixture through heat exchanger fill neck until coolant appears at
c. Close bleeder valve securely.
d. Continue filling until coolant level is into filler neck and begins to flow into coolant
Avoid seawater pickup pump impeller damage. DO NOT operate engine without
water being supplied to seawater pickup pump.
Front of engine should be higher than rear to purge trapped air out of the system
during initial filling. This will minimize the possibility of air being trapped in the
closed cooling section which can cause engine to overheat.
IMPORTANT: Coolant flows rapidly. Higher idle speeds increase dispersion of
trapped air into system making it more difficult to purge trapped air. Operate at idle
during filling and air purging when specified.
2. Start engine and run at IDLE.
Index
Page 6B-16
a - Hex Head Bleeder Valve
bleeder valve opening.
recovery bottle plastic tubing.
CAUTION
a
CAUTION
CAUTION
SERVICE MANUAL NUMBER 24
75598
90-861327--1 OCTOBER 1999