Regal 53 SC Owner's Manual page 219

Chapter 5
When the coolant temperature is below the operating
range of the thermostat, engine coolant is bypassed back
to the inlet of the water pump. When the coolant tem-
perature is below the operating range of the thermostat,
engine coolant is bypassed back to the inlet of the water
pump. When the engine coolant temperature reaches the
operation range, the thermostat opens, sealing off the by
pass, forcing engine coolant to fl ow to the heat exchanger.
The cooling system is designed to use a pressure cap to
prevent boiling of the coolant. If cap replacement is nec-
essary it is important to match the original cap specifi -
cations. A malfunctioning cap can result in the loss of
coolant and an engine overheating condition.
The expansion tank creates positive pressure in the cool-
ing system to control coolant boiling. The expansion tank
removes air bubbles from the coolant. It contains a cool-
ant reserve to help with small leaks without overheating
the engine and the system uses a coolant level sensor that
warns of low coolant condition.
The heat exchanger is a two pass, tube design and is lo-
cated on the exhaust side of the engine. The end cover
plates are removable for cleaning the tubes; the cooler
bundle is not removable. A sacrifi cial plug is located in
the front cavity of the heat exchanger sea water passage.
The engine coolant fl ows from the thermostat housing
outlet into the top front of the heat exchanger and is di-
rected over the tubes by baffl es. The engine coolant exits
the cooler at the bottom rear of the heat exchanger. The
engine coolant is returned to the engine coolant pump
inlet via a transfer tube. The coolant sea water enters the
bottom rear of the heat exchanger cavity and is diverted
to the lower half of the cooler tubes by a divider plate
in the cavity. The sea water fl ows through the tubes to
the front, nondivided cavity. The sea water then fl ows
through the tubes on the upper half of the cooler and is
discharged out of the top rear of the heat exchanger, and
into the outer shell of the exhaust elbow. The sea water is
then discharged overboard.
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