Chapter 11

Cooling Systemspage 191

Cooling Systems Types

• Air cooling• Liquid Cooling• Mixture Air/Liquid

Principles of Engine Cooling• Efficiency and

life of engine• Burned gasses

3600 F• Loss of heat

through cylinder walls

• 1200 F to 350 F • 100 F by outer

fins

COOLING SYSTEMS• Heat Energy From Combustion

1. Cooling and Lubrication systems 33%

2. Exhaust system 33%3. Engine power 25%4. Frictional loss 5%

How Air Cooling Works

• heat passes through cylinder wall• air passes by fins• guided by baffles• Conduction – through a material material• Convection – solid to gas transfer• Radiation – gives off heat

Parts of an Air Cooled system

• Fly Wheel• Shrouds• Fins

How Exhaust Cooling Works

• 1/3 heat lost through exhaust (muffler) 1200 F• Blocked muffler• Broken muffler

How Water Cooling Works

• Passage surrounds cylinder (water jacket)• No fins• water/antifreeze mixture• protects freezing• raise boiling point• prevent corrosion

Parts of the Liquid Cooled System

• Radiator• Water pump• Water Jacket• Hoses• Fan• Shroud• Belt• Thermostat

Radiator

• Tubes• Fins• Transfers heat

– coolant >air

Radiators

• Caries water through tubes• Air travels through fins• Together make RADIATIOR CORE• Cross flow & Down flow

Water Pumps• Moves coolant• Boat at lower end of motor• Driven by crankshaft• Types

– sliding vane– rotor– plunger– vari-volume

Radiator Cap

• Pressurize• Pascal’s Law• 1 psi = 3 F

Observing Thermostat Operation

• Opens at preset temp. • Rating stamped on thermostat• Holds coolant in block• Opens to cool

Outboard Water Circulation Systems

• Pressure-vacuum water flow system• propeller causes pressure & vacuum• Centrifugal force• no moving parts (propeller)

How Oil Cooling Works

• Oil collects dirt and particles• Removes heat (5%)