4-7
MAINTAINING THE ENGINE COOLING
SYSTEM
Refer to Table 4-1 for scheduled maintenance.
Cooling System Overview
The engine is cooled by a pressurized, closed-loop
liquid cooling system in which coolant is pumped
through passages in the engine block, head and ex-
haust manifold (Figure 4-4, 4-5or 4-6). Heat is car-
ried away from the coolant by a keel cooler or raw
water (sea water) heat exchanger. A gear-driven
raw water pump is provided if the genset has a heat
exchanger or wet exhaust.
Keel Cooler: A keel cooler, when provided, is part
of the pressurized, closed-loop liquid cooling sys-
tem through which the coolant flows.
Heat Exchanger: When a heat exchanger is pro-
vided, raw water (the floatation water) is pumped
through tubes in the heat exchanger to cool the en-
gine coolant. The water is then passed through a
hose into the exhaust-water mixer to cool the ex-
haust gases. The raw water is expelled from the
boat along with the exhaust gases.
Recommended Coolant Mixture
See ENGINE COOLANT (p. 3-1) for recommenda-
tions.
Replenishing Normal Coolant Loss
Check coolant level in the recovery tank before the
first startup of each day and, if necessary, refill to
COLD when the engine is cold or to HOT when it is
running. The recovery tank is designed to maintain
coolant level, not to fill the system. If the tank is
empty, check for and repair any coolant leaks and
refill the system through the fill neck on the engine.
Pressure Cap
Replace the pressure cap every two years (seals
deteriorate and leak). Proper cooling system pres-
sure (10 psi) is essential for optimal engine cooling
and minimal coolant loss.
Coolant Hoses
Check for and replace hoses that leak or are dam-
aged.
Draining and Cleaning Cooling System
Have towels and containers ready to wipe up, col-
lect and properly dispose of the coolant. Disconnect
the negative (−) cable at the battery to prevent the
engine from starting and let the engine cool before
removing the pressure cap.
WARNING
Accidental or remote starting can
cause severe personal injury or death. Discon-
nect the negative (−) cable from the battery to
prevent the engine from starting.
Hot coolant spray can cause severe burns. Let
the engine cool before releasing the pressure
cap or removing the drain cap.
Remove the pressure cap and open the block and
heat exchanger drain valves (Figure 4-4, 4-5or 4-6)
and drain the coolant into suitable containers for dis-
posal in accordance with the local regulations for
hazardous substances.
Drain or flush a keel cooler in accordance with the
manufacturer’s instructions.
Use radiator cleaning chemicals to clean and flush
the cooling system before refilling with fresh cool-
ant. Follow the cleaner manufacturer’s instructions.
CAUTION
Filling a hot engine with cold water
can cause cracks in the manifold, head and
block. Follow the manufacturer’s instructions
for cleaning and flushing.
Redistribution or publication of this document,
by any means, is strictly prohibited.
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