Indmar Marine Engines
6-13
Fresh Water Cooling – Full System – Salt Water
Series Engines
Some fresh water cooling systems are referred to as full
systems. A full fresh water system includes the exhaust
manifolds as part of the system that is cooled with anti-
freeze. Most commonly, a block-off plate is installed
between the exhaust manifolds and exhaust risers and
the risers are cooled with raw water.
Even though the engine has a full closed cooling system,
it still uses raw water in a heat exchanger to remove the
heat from the closed portion of the system. The raw
water side of the system needs to be flushed regularly
with fresh water to keep the whole system functioning
properly.
Because the risers are exposed to salt water they are
subject to corrosion. These risers must be inspected by
your dealer annually and replaced as required. It is not
unusual to have to replace these risers every two years
on boats used exclusively in salt water.
Some Full Fresh Water Cooled engines equipped with
ETX-CAT one piece exhaust manifolds do not have sepa-
rate exhaust risers. Full FWC systems utilizing those
manifolds use anti-freeze in the complete manifold/riser
assembly and will not have the riser corrosion issues
associated with the two piece manifold/riser assemblies.
Fresh Water Cooling – All Systems
All fresh water cooling systems, whether they are half or
full systems, must be inspected and maintained annually,
usually during winterization.
Heat Exchanger – Remove the end caps to drain and
inspect the heat exchanger. Clean out any debris. Make
sure you inspect the end caps for contour and cracks
and replace the neoprene gaskets before putting the
boat back in service. If you find rubber bits in the
exchanger, check the raw
water pump impeller. Note
that if you use a clean-out
rod, it should be softer than
the copper tubes, and
should not be used to dis-
lodge materials which are
firmly stuck to the tube sur-
face, as this could damage
the tubes. The rod will assist
in cleaning out bits of grass,
zinc, shells, and similar
materials which are just
lodged in the tubes.
Zinc Anodes – The sacrificial zinc anodes frequently
spall, and there will probably be zinc bits in the exchang-
er which should be cleaned out. Inspect the zinc anode
often during use and replace when it is 3/4" (19 mm)
or less.
SACRIFICIAL ANODE
REPLACE IF ANODE IS
3/4" (19 mm) OR
LESS IN LENGTH
INDM-B007
Figure 6.7 – Sacrificial
Anode
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Summary of Contents for 5.7L MPI
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