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INSTALLATION
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COOLANT SYSTEM
ELECTRICAL
ENGINE BEDS
ENGINE MOUNTS
EXHAUST SYSTEM
FRONT PTO
FUEL SYSTEM
HOT WATER CYLINDER
OVERFLOW BOTTLE
OVERVIEW
PANELS
PROPELLER
RAW WATER SYSTEM
SEA TRIAL

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Yanmar Pleasure Boat Marine Engine Help

Coolant System

WARNING: Do not remove the heat exchanger (radiator) cap while the engine is hot unless you are within helicopter range of the local hospital burns unit! If you didn't heed this warning, don't scream too loudly.

Fresh water circuit diagram

Component Description

The components that make up the coolant system are in the drawing above.
The Overflow Bottle and Hot Water Cylinder are part of the Coolant System and have been given their own page to reduce the size of this one.
The coolant circuit in the schematic above is in red, the raw water circuit is in blue.
Operation: The coolant pump (aka freshwater pump) circulates the coolant, via a bypass, through the cylinder block and cylinder head and back to the thermostat housing. If the coolant is below 750C the thermostat remains closed and the coolant is continuously circulated through the block and head via the bypass. When the temperature of the coolant rises above 750C the thermostat begins to open, the bypass begins to close, and the coolant is pumped through the heat exchanger. By the time the temperature is around 88 - 900C the thermostat is fully open and the bypass is closed. The raw water in the 'blue' circuit absorbs the heat from the heat exchanger and carries it out of the engine, usually via the exhaust.
Fresh water coolant: aka anti-freeze, should be installed in every engine regardless of location and climate. It is a 50/50 mixture of coolant and deionised water, (fresh water with a neutral pH / clean rain water ) to protect against internal corrosion and cavitation erosion within the fresh water cooling system. It also lowers the freezing point (-36oC deg) and raises the boiling point (+129odegC) of the coolant, thereby widening the temperature parameters the engine can safely operate within.

Installation Tips

In turbocharged engines use only:
Havoline® Extended Life Coolant, DEX-COOL® Code number 7994, colour: ORANGE
You can safely use this product in any YANMAR fresh water cooled engine, follow the coolant manufacturers instructions for servicing. TEXACO No, I dont work there or know anyone that does, I just know what works!
Use de-ionized water (or clean rain water) and coolant, or buy the 50/50 premixed coolant.

Except in an emergency do not top up a system with water only. If you had to add water only to the coolant, replace the entire coolant package as soon as practicable.

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