SECTION
R
COOLING
SYSTEM
(EXTERNAL)
1.
DESCRIPTION:
Wes~erbeke.marine
diesel engines are
equlpped
wlth fresh water cooling.
Transfer of heat
from
engine fresh
water to sea water
is
accomo1ished
in a heat exchanger, similar in func-
tion to
an
automotive radiator.
Sea
water
flows
through the tubes of the
heat exchanger while fresh water
flows
around
the tubes.
The
sea
water
and
fresh water never
mix
with the
result
that
the cooling
water passages in the engine stay
clean.
2.
FRESH
WATER
CIRCUIT:
Heat
rejected during combustion,
as
~ell
as
heat developed
by
friction,
lS
absorbed
by
the fresh water
whose
flow
is
created
by
a fresh water
cir-
culating
pump.
The
fresh water
flows
from
the engine through a fresh water
cooled exhaust manifold, a heat ex-
changer, in
most
cases
an
oil cooler
and
returns to the suction side of '
the fresh water circulating
pump.
The
flow
is
not necessarily in
this
order in every
model.
When
starting
a cold engine,
most
of the external
flow
to the heat exchanger
is
pre-
vented
by
the closed thermostat.
Some
amount
of by-pass
is
maintained
to
~revent
overheating in the exhaust
manlfold.
As
the engine
warms
up
the
thermostat begins to
open
up
a11~wing
full
flow
of engine fresh water thru
the external cooling system.
3.
SEA
WATER
CIRCUIT:
The.s~a
wa~er
flow
is
created
by
a
posltlVe dlsp1acement
neoprene
inpe11e--
pump
(gear
pump
in certain special
cases).
Normally
the
pump
draws
sea
water
directly
from
the
ocean
via the
sea
cock
and
sea water
strainer.
Some-
times a transmission oil cooler, or
pehaps
a V drive will
be
piped
on
the
suction side of the sea water
pump.
Gen~rally
it
is
better
to
have
as
few
devlces
on
the suction side of the sea
wa~e~
pum~
a~
possible to preclude
prlmlng
dlfflculties.
Usually sea
water
flows
directly
from
the
dis-
charge of the sea water
pump
to the
heat exchanger sea water
inlet.
After
passing through the tubes of the heat
exchanger,
the sea water
may
enter a
transmission oil cooler
if
present
and
if
sea water cooled. Ultimately,
the sea water enters a water injected,
wet
exhaust system, the
most
popular
type of exhaust
system
in use.
In
the case of larger engines the sea
~ater
flow
is
divided prior to enter-
lng
the exhaust
systems
so
that
a
portion
is
dumped
directly
overboard
and
a portion
is
used
to
cool
the
exhaust system. Full sea water
flow
entering the exhaust system
would
create unnecessary exhaust
back
pressure.
4.
SEA
WATER
PUMP:
The.s~a
wa~er
pump
is
self
priming
and
posltl~e
dlsplacement.
It
is
a rotary
pump
wlth a nonferrous housing
and
a
neoprene
impeller.
The
impeller
has
flexible
vanes
which
wipe
against a
curv~d
cam
plate within the impeller
houslng, producing the
pumping
action.
On
no
account should
this
pump
be
run
dry.
There
should
always
be
a spare
impeller
and
impeller cover gasket
aboard.
5.
SEA
WATER
PUMP
IMPELLER
REPLACEMENT:
The
following instructions are general
and
indicative only. Specific instruc-
tions
where
applicable
may
be
packaged
with
your
replacement impeller.
a.
Remove
the front cover taking care
to salvage the gasket.
b.
Remove
the impeller
by
pulling
straight
outwards, parallel to
the
pump
shaft.
This
is
best
done
with a pair of
pliers
ap-
plied to the impeller
hub.
c.
Coat
the replacement impeller
and
the
chamber
into
which
it
mounts
with grease.
d.
Carefully align the impeller
key
way,
or other locking
mechanism,
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