Mercury 90 Service Manual

90-830234R3 DECEMBER 1997 POWERHEAD - 4-45
Cylinder Cover, Exhaust Divider Plate
and Exhaust Cover
• Thoroughly clean cylinder cover and gasket sur-
faces.
• Inspect cylinder cover. Check for cracks which
could cause water leakage.
• Replace cylinder cover as necessary.
• Thoroughly clean gasket surfaces of exhaust di-
vider plate and exhaust manifold cover.
• Inspect exhaust divider plate and exhaust
manifold cover for grooves, cracks or distortion
that could cause leakage. Replace parts as
necessary.
a
b
c
a - Cylinder Cover
b - Divider Plate
c - Exhaust Cover
Thermostat
Wash thermostat with clean water. Using a thermo-
stat tester, similar to the one shown, test thermostat
as follows:
• Open thermostat valve, then insert a thread be-
tween valve and thermostat body. Allow valve to
close against thread.
• Suspend thermostat (from thread) and thermom-
eter inside tester so that neither touches the con-
tainer. Bottom of thermometer must be even with
bottom of thermostat to obtain correct thermostat
opening.
• Fill thermostat tester with water to cover
thermostat.
• Plug tester into electrical outlet.
• Observe temperature at which thermostat begins
to open. Thermostat will drop off thread when it
starts to open. Thermostat must begin to open
when temperature reaches 5 F (3 C) above
designated stamping on bottom of thermostat.
• Continue to heat water until thermostat is com-
pletely open.
• Unplug tester unit.
• Replace thermostat, if it fails to open at the speci-
fied temperature, or if it does not fully open.
51087

Mercury 90 Specifications

General

Brand	Mercury
Model	90
Category	Outboard Motor
Language	English