Cooling System - Volvo Penta 3.0GS/SX Owner's Manual

Cooling System

The cooling system is a seawater system (a freshwater system is available as an accessory for certain types of
engine). The engine seawater pump (mounted on front of the engine) sucks in water through the water inlets lo-
cated on both sides of the lower gear unit. Water pumped to the engine by the seawater pump is circulated th-
rough the engine by the engine circulating pump. A thermostat determines the amount of water to be taken in,
recirculated and discharged to control engine operating temperatures. Water is discharged through an idle ex-
haust relief and with exhaust through the propeller hub. A temperature gauge located on your boat instrument
panel will indicate if the engine overheats. Do not operate engine without thermostat.
IMPORTANT If engine should overheat, turn off engine, tilt drive up and look for obstructions to water pick-
up. Lower drive unit and run engine again at 1500 RPM in neutral and check temperature gauge to verify
condition. If overheating still occurs, return to port at low RPM to prevent excessive overheating and engi-
ne damage. See your Volvo Penta dealer for service assistance.
If there is a risk of frost the cooling system must be drained.
When laying up the boat for the winter it is important that the cooling system be flushed with freshwater so
that deposits do not dry and to prevent the build-up of salt crystals.
B
C
A
Draining cooling system
Perform this procedure with boat out of water. It
will prevent damage to cooling system compo-
nents if temperature drop below freezing. When
draining the engine, raise or lower the bow of the
boat to position the engine in a level altitude. This will
provide for complete drainage of the block and mani-
fold. If the bow of the boat is higher or lower than the
stern, some water may be trapped in the block.
4.3, 5,0 and 5.7 models
Front
Disconnect long hose (A) at thermostat housing.
Lower alongside block and drain completely.
Disconnect and drain large hose (B) at water
pump housing.
Drain the small water by-pass hose between fuel
reservoir and the top of thermostat housing. Dis-
connect at the reservoir side of the check valve.
Blow out water in both directions. Inspect check
valve for debris, then reassemble.
Front, 4.3 models only
Remove intake manifold drain plug (C) and drain mani-
fold.
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