Service manual

SEAWATER COOLED MODELS
SERVICE MANUAL NUMBER 26
90-861329--1 MARCH 1999 Page 6A-5
Thermostat
Removal
1. Drain water from cylinder block and exhaust manifold.
2. Disconnect hoses from thermostat cover.
3. Remove thermostat cover attaching bolts and lockwashers.
4. Remove thermostat from thermostat housing or cover.
73572
a
b
140° Thermostat Housing Shown
a-Thermostat Cover
b-Attaching Bolts
Testing
1. Clean thermostat in soap and water to remove any deposits or debris.
2. Inspect for corrosion or other visible damage.
3. If thermostat is suspected of producing insufficient engine temperature, check
thermostat for leakage by holding it up to a lighted background. Light leakage around
the thermostat valve indicates that thermostat is not closing completely and should be
replaced. (A small amount of leakage one or two locations around the valve perimeter
is acceptable.)
4. Check opening and closing temperature of the thermostat (using a tester similar to one
shown below), as follows:
a. Fill tester to within 1 inch (25 mm) of top with tap water. DO NOT use distilled water.
b. Open thermostat valve and insert nylon string. Position thermostat on string so that
it will be just below water level when suspended, then allow valve to close. Suspend
thermostat in water.
Index