Technical data

8. THERMOSTAT
Generally, thermostats are of two types. One is simply a choking device which opens and closes as the
engine temperature rises and falls. The second type has a by-pass mechanism. Usually this is a disc on
the bottom of the thermostat which moves downward to close off an internal by-pass passage within the
head. Both types of thermostats, from 1980 onwards, have a hole punched through them to serve as a
by-pass while the engine is warming up. This prevents overheating in the exhaust manifold during engine
warm-up. Replacement thermostats must be equal in this design characteristic.
When replacing a thermostat, be sure that it is rotated so as to not strike the thermostat housing,
projections inside the head, temperature senders or temperature switches which may be installed close to
the thermostat. Also insure the by-pass hole is not blocked by any part of the housing. A thermostat can
be checked for proper operation by placing it in a pan of cold water and then raising the temperature of
the water to a boil. The thermostat should open noticeably (with travel on the order of 1/4" - 1/2") and be
fully opened when the water is boiling.
9. ENGINE LUBE OIL COOLER
Lubricating oil carries heat away from the engine bearings and other friction surfaces. The oil
circulates from the lube oil pump, through the engine, through the engine oil cooler, and back to the oil
pump. The oil cooler may be cooled either by engine fresh water or by sea water.
10. TRANSMISSION OIL COOLER
Certain transmissions require oil cooling. In these cases, the transmission oil cooler is usually cooled
by sea water.
Normally, sea water enters this cooler after exiting the heat exchanger, but not always.
11. EXHAUST MANIFOLD - EXTRUDED TYPE
REMOVAL
Removal of the exhaust manifold from the engine should be done as a complete assembly in the
following manner.
a. Drain the engine and cooling system of all coolant.
b. Remove the exhaust connection.
c. Loosen and remove all hose connections to the manifold.
d. Loosen and remove the nuts or bolts attaching the manifold assembly to the cylinder head.
e. Remove the manifold from the cylinder head as a complete unit.
SERVICING
a. Remove the exhaust elbows from the lower surface of the manifold. Clean and inspect for
cracks and defects. Replace as needed.
b. Remove exhaust nipples, elbows and plugs from the manifold.