Yanmar 1GM User Manual page 71

LAY-U P AND FITTING OUT
Heat
--'l--T~'
exchanger
2. On 3GM , 3GM30, 3HM and 3HM35 engines, open the
drain on the underside of the exhaust manifold (Fi !!:u re 1,
typical).
3. Open the drain on the cylinder block (F igure 2, typi-
cal).
4. Remove the lower end of all cooling system hoses
from the engine, pump and exhaust manifold. Lower the
hoses and allow them to completely drain. Reconnect the
hoses and clamp securely.
,VOTE
On IGM and
IGMIO
engines. access is re-
stricted to the upper water pump cover
sere",·:
If
a suitable tool is not available, it
may be necessary to remove the crankshaft
pulley jor access
to afl of the water pl/mp
cover screws .
65
5. Loosen the cover screws on the seawater pump (Fig -
u re 3, typica l) and drain any water in the pump. lf thc gas-
ket is damaged. remove the cover and install a new gasket
and the cover.
6. Allow the cooling system to drain completely, then
close all drains.
Adding antifreeze
The following procedure pertains to seawater cooling
systems and is designed to provide additional protection
against damage due to freezing temperatures while the
boat is in storage.
C.AUTION
Do not nm the engine after performing the
storage service procedure tnat fotlows. Be-
fore
returning the hoat
to
service, drain the
seawater cooling system as described in this
chapter.
I. Refer to Chapter Eight to remove the thermosta t and
gasket. Discard the gasket .
2. Make sure the scacock or water inlet to the seawater
pump is closed .
3. Pour a 50/50 solution of pure soft water and ethylene
glycol antifreeze through the thermostat hole into the en-
gine until the cylinder head, block and manifold arc full,
4. Reinstall the thermostat with a new gasket.
Freshwater (Closed) Co oling Syste m
The freshwater section ofa cooling system need not be
drained during winter months, provided it is filled with a
50/50
solution of pure soft water and ethy lene glycol anti-
freeze. However, if draining the freshwater cooling sys·
tern is necessary, usc the following procedure.
Note that the follow ing procedures address the freshwa-
ter and seawater sections of the cooling system separately.
If the freshwate r portion is not being drained, follow the
draining procedure for the seawater section.
Fre shwater (cloud) cooling section
I. Place containers under the drains, if space permits.
This will prevent coolant from draining into the bilge.
2. Remove the pressure fill cap from the heat exchanger
(Figure 4).
WARNING
Ethylene glycol is
WI
environmental toxic
waste that cannot he legally flushed down a
drai n or poured on the ground. Put it in suit-
4