Engine Maintenance Chapter 1 What Makes the Boat Go

2 Objectives for the Student 1.Have a good grasp of the components of the modern marine propulsion system 2.Have an understanding of the principles of the modern marine engine, both two stroke and four stroke 3.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: Needed for combustion: fuel fuel air (oxygen) air (oxygen) ignition source ignition source

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

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

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

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

8 The Marine Engine Exhaust Exhaust spent gases are expelled spent gases are expelled

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

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

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

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

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

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

15 Displacement Engine Displacement Engine Displacement The total volume of one cylinder’s displacement, times the number of cylinders The total volume of one cylinder’s displacement, times the number of cylinders Displacement = n V = n  r 2 h where n = number of cylinders V = volume of one cylinder

16 Displacement Example: Chevrolet 350 V-8 Example: Chevrolet 350 V-8 Bore = 4.00 inches Bore = 4.00 inches Stroke = 3.48 inches Stroke = 3.48 inches Displacement = n V = n  r 2 h Displacement = n V = n  r 2 h Displacement = 8 x x (2.00 inches) 2 x 3.48 inches Displacement = 8 x x (2.00 inches) 2 x 3.48 inches Displacement = 350 inches 3 or 350 cubic inches or 350 cubic inches displacement or 350 CID Displacement = 350 inches 3 or 350 cubic inches or 350 cubic inches displacement or 350 CID

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

18 Engine Compression Compression Ratio Compression Ratio The cylinder’s total volume at BDC, divided by volume at TDC 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 Compression Ratio = V / v V = 17 cubic inches V = 17 cubic inches v = 2 cubic inches v = 2 cubic inches V / v = 17/2 = 8.5:1 V / v = 17/2 = 8.5:1

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

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

22 The Marine Drive System Outboard Systems Power Head Intermediate Housing Lower Unit

23 The Marine Drive System Inboard Systems

24 The Marine Drive System Stern Drive (I/O) Systems

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

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

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

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