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Engine Maintenance

Engine Maintenance. Chapter 1 What Makes the Boat Go. Objectives for the Student. Have a good grasp of the components of the modern marine propulsion system Have an understanding of the principles of the modern marine engine, both two stroke and four stroke

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Engine Maintenance

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  1. Engine Maintenance Chapter 1 What Makes the Boat Go

  2. Objectives for the Student • Have a good grasp of the components of the modern marine propulsion system • Have an understanding of the principles of the modern marine engine, both two stroke and four stroke • Have an understanding of the general troubleshooting methodologies that can be used and repair work that needs to be done

  3. The Marine Engine • Needed for combustion: • fuel • air (oxygen) • ignition source

  4. The Marine Engine • A compressed fuel/air mixture is ignited • Burning mixture increases in temperature and pressure • Expansion of gas is converted to linear piston motion • Crank converts linear motion to rotary motion

  5. Intake fuel/air enters the combustion chamber The Marine Engine

  6. Compression mixture is compressed within the cylinder The Marine Engine

  7. Power compressed charge is ignited to move the piston downward The Marine Engine

  8. Exhaust spent gases are expelled The Marine Engine

  9. The Diesel Engine • Intake • air enters the combustion chamber

  10. The Diesel Engine • Compression • air is compressed to high temperature

  11. The Diesel Engine • Power • fuel is injected and autoignites

  12. The Diesel Engine • Exhaust • the spent gases are expelled

  13. Displacement • Cylinder Displacement • The total volume of air that can be moved in one engine cycle for one cylinder • Bore • Diameter of the cylinder • Stroke • Total piston travel from TDC to BDC

  14. r h Displacement • Volume of a Right Circular Cylinder • V = p r2 h • where • V = volume • p = 3.1416 • r = radius (1/2 diameter) of cylinder • h = height of the cylinder (stroke)

  15. Displacement • Engine Displacement • The total volume of one cylinder’s displacement, times the number of cylinders • Displacement = n V = n p r2 h • where • n = number of cylinders • V = volume of one cylinder

  16. Displacement • Example: Chevrolet 350 V-8 • Bore = 4.00 inches (10.16 cm) • Stroke = 3.48 inches (8.84 cm) • Displacement = n V = n p r2 h • Displacement = 8 x 3.1416 x (2.00 inches)2 x 3.48 inches • Displacement = 350 inches3 or 350 cubic inches or 350 cubic inches displacement or 350 CID • Displacement = n V = n p r2 h • Displacement = 8 x 3.1416 x (5.08 cm)2 x 8.84 cm • Displacement = 5735 cc or 5.7 liters

  17. Size Matters • Engines of Greater Displacement Generally Deliver More Horsepower • More fuel/air consumed per stroke • More heat released • More power produced

  18. Engine Compression • Compression Ratio • The cylinder’s total volume at BDC, divided by volume at TDC • Compression Ratio = V / v • where • V = volume at BDC • BDC = bottom dead center • v = volume at TDC • TDC = top dead center

  19. Engine Compression • Compression Ratio = V / v • V = 8.8496 cubic inches (145 cc) • v = 1.0411 cubic inches (17 cc) • V / v = 8.8496 / 1.0411 = 8.5:1 • V / v = 145 / 17 = 8.5:1

  20. Horsepower and Torque • Horsepower • measure of work • 1 hp = 745 watts • Torque • measure of rotational force • pounds-foot (lb-ft) • Newton-meter (Nm)

  21. The Marine Drive System • Three Basic Types of Marine Drives: • Outboard • Inboard • Stern Drive, also known as Inboard/Outboard or I/O drive

  22. The Marine Drive SystemOutboard Systems Power Head Intermediate Housing Lower Unit

  23. The Marine Drive SystemInboard Systems

  24. The Marine Drive SystemStern Drive (I/O) Systems

  25. Thrust Units • Propeller • 2-4 blade (inboards) • 3-6 blades (outboards) • Pitch • measure of advance (one rotation through a solid object) • Diameter • diameter of a circle that describes the blade tips

  26. Thrust Units • Water Jet • Internal impeller • Good for shallow water operation • Directs thrust using steerable nozzle and reverse gate

  27. General Troubleshooting Methodology • Check the Obvious • Check the Easy • Check Systematically • Make No Erratic Adjustments

  28. Remember… You should be able to identify problems and explain them to a mechanic

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