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S08 MAINTENANCE
COOLING SYSTEM
OVERVIEW
The cooling system cools the engine in order to main-
tain a proper operating temperature and to prevent
overheating. On some engines, the cooling system also
cools the fuel, the oil or the air intake. The cooling sys-
tem is built around two circuits:
• The COOLANT CIRCUIT which is the engine internal
cooling system. It is a closed-circuit in which coolant
flows and cools the engine.
• The RAW WATER CIRCUIT which cools the coolant via
an heat exchange with raw water. Nanni engines are
delivered as standard with an heat exchanger, in which
the coolant is cooled by heat exchange with raw water
taken from a sea cock. A Keel Cooling system can also
be used to cool the coolant instead.
A thermostat maintains the coolant at a proper and
constant operating temperature. With thermostat con-
trol, the coolant only enter the heat exchanger when the
engine reach the appropriate temperature of the engine.
Principle of operation of water cooling with heat
exchanger on an engine.
CAUTION !
Engines designed with an heat exchanger are not sui-
table for a Keel Cooling System (case of T and Z Nanni
engines series).
Operating the engine without coolant or raw water sup-
ply, even for few seconds, will lead to a complete engine
breakdown.
Instead of proper mix coolant, raw clean water can only
be used in case of emergency and for the shortest time
possible. As soon as back to shore, get in touch with
the nearest Nanni representative or seasoned marine
shipyard or workshop. Please refer to the Fluids section
for complete information.
• Always use coolant made of 50% antifreeze with
anticorrosion additive and 50% of clean water. The
antifreeze protects the engine against internal
corrosion.
• This mix must be used all year around, even if there
is no risk of frost.
• Never use water alone to completely ll the coolant
system.
Please refer to the Fluids section for complete
information.
FLEXIBLE DUCTS
Follow closely the maintenance schedule to watch
the state of the flexible ducts and especially the ones
remaining hidden during a quick check.
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