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Engine Maintenance

Engine Maintenance. Chapter 2 Inboard Spark Ignition Engines Part 1. Objectives for the Student. Have a good understanding of the component parts of the marine gasoline engine and how these parts work together to perform the useful function of propelling the boat

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Engine Maintenance

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  1. Engine Maintenance Chapter 2 Inboard Spark Ignition Engines Part 1

  2. Objectives for the Student • Have a good understanding of the component parts of the marine gasoline engine and how these parts work together to perform the useful function of propelling the boat • Have knowledge of the fuel, cooling, exhaust, lubrication, ignition, and electrical systems needed for the engine to function properly

  3. What’s Covered in This Chapter • Engine Components • engine block • cylinders and cylinder heads • crankshaft, pistons, and connecting rods • valve train • manifolds • Associated Systems Required for Operation • fuel systems • cooling systems • exhaust systems • lubrication systems • ignition systems • electrical and starting systems

  4. Engine Components • 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. Engine Components • Engine Block • largest single component of an inboard spark ignition engine • principle purpose Is to enclose the cylinders and provide support for the crankshaft • may be either Inline, Vee, or Opposed in design A Vee Type Engine Block. The Crankshaft Is Not Shown

  6. Engine Components • Cylinders • perfectly round holes in the engine block • sides are finely finished to a smooth surface • pistons ride up and down inside the cylinders Cut Away of an Engine Block to Show the Cylinders.

  7. Engine Components Diagram of a 6 Cylinder Inline Engine Block with Last Two Cylinders Cut Away • Engine Cylinder Configurations • Inline • Vee • Opposed Cut Away Drawing of a V-8 Engine The Opposed Engine is basically a flattened vee design. It is sometimes referred to as a "pancake engine"

  8. Crankshaft • Primary Rotating Component • Converts Reciprocating Motion to Rotary Motion • High-Tensile Steel

  9. Piston, Rings, Connecting Rod • Pistons • pushed down by burning fuel • top is part of the combustion chamber • Rings • seal piston within cylinder • Connecting Rods • connect piston to crankshaft

  10. Engine Components • Flywheel (on transmission end of crankshaft) • maintains momentum between power strokes • Vibration Damper (on other end of crankshaft) • offsets torsional vibration

  11. Oil Pan • Oil Reservoir on Bottom of Engine Block

  12. Camshaft • Provides Timing • intake and exhaust valves • either spark plug or fuel injector • Rotates (chain or gear driven) • 4-cycle engines: at half crankshaft speed • 2-cycle engines: at crankshaft speed

  13. Valves • Intake and Exhaust Valves Open into Cylinders • Most are Opened by Camshaft Pressure and Closed by Strong Spring

  14. Manifolds • Intake • carburetor to cylinder head (induction) • Exhaust • exhaust block (exhaust valves) to muffler • exhaust elbow is raw water cooled

  15. Summary – Engine Components • Major Marine Engine Components • crankcase or cylinder block • cylinders and cylinder heads • crankshaft • pistons, rings, connecting rods • flywheel, vibration damper • oil pan • camshaft • valves • manifolds

  16. Associated Systems • Fuel System • Cooling System • Exhaust System • Lubrication System • Ignition System • Electrical and Starting Systems

  17. Fuel System • Gasoline is the Fuel for Inboard Spark Ignition Engines • Gasoline is Mixed with Oxygen (Air) Before It Enters the Combustion Chamber • Work Done Depends on Heat Obtained from Burning the Fuel

  18. Fuel System • Gasoline is Ranked by Octane Number • Higher octane number burns at higher temperature • Higher octane number provides a stable, controlled burn • Low octane sometimes ignites prematurely, resulting in “pinging” or “knocking”

  19. Fuel System Safety Precautions With Gasoline • When Refueling • close all hatches and extinguish all flames • good contact between nozzle and fuel pipe • Fuel Tank • properly installed and well vented • periodically inspected for fuel leaks • Bilges • run blowers for at least 5 minutes before starting engine • before starting gas engines, sniff bilge for gas fumes

  20. Simplified Carburetor Fuel System • Components of the Fuel System • carburetors or fuel injection system • fuel pump • fuel filter • Carburetor • vaporizes gasoline • throttle controls fuel volume

  21. Fuel System • Electronic Fuel Injection • delivers more power than carburetors • fuel is metered into the air intake stream • controlled by several sensors

  22. Intake Discharge Fuel System • Fuel Pumps • mechanical low pressure diaphragm • may be electric

  23. Fuel System • Flame Arrestors • grid of closely space metal louvers, which allow free air flow but immediately extinguish any flame • Flame Arrestors are Required by Federal Law (all boats manufactured after 1948) • even on fuel injected gasoline engines

  24. Cooling Systems • Proper Cooling • temperatures above: • 400 F (204 C) may break down lubrication • 500 F (260 C) may burn valve seats • aluminum begins to lose its strength • Water in Water Jacket Removes 90% of Waste Heat • Lubrication in Engine Removes 10% of Waste Heat • Must Have Airflow Outside of Engine • Overcooling May Cause Poor Lubrication and Alter Engine Clearances

  25. Cooling Systems • Direct (or Open) Cooling • engine is cooled by seawater • disadvantage: engine exposed to raw (salt) water • Indirect (or Closed) Cooling • engine is cooled by coolant • mixture of antifreeze and clean (distilled) water • coolant is then cooled by seawater in heat exchanger • disadvantage: requires heat exchanger

  26. Cooling Systems Direct Simplified Schematic

  27. Cooling Systems Indirect (note heat exchanger) Simplified Schematic

  28. Cooling Systems Keel Cooler

  29. Impeller (Rotary) Gear Centrifugal Cooling Systems • Pumps • Normally belt driven from engine

  30. Cooling System • Thermostat • temperature-sensitive device used to maintain correct operating temperature • Ratings: 145 F (63 C) and 195 F (90 C) • fully open at approximately 20 F (11 C) over rating

  31. Exhaust Mixing Elbow Exhaust Systems • Exhaust Gases are Extremely Hot and Poisonous • Two Types of Exhaust: Wet and Dry • wet is preferred and safest • Exhaust System Must Not Ingest Water • anti-siphon break (vacuum valve)

  32. Elbow below water line; may permit siphoning of seawater into engine Elbow above water line; no siphoning effect Typical Inboard Powerboat Typical Sailboat Exhaust Systems • Sailboat Exhaust Risers are Normally Below Waterline (especially when heeling) • In Such a Case, an Anti-Siphon Valve is Needed to Let Air into the Exhaust Line (break vacuum)

  33. Lubrication Systems • Purpose of Oil • Characteristics of Oil • Lubrication Systems • Oil Pumps • Oil Filters • Compounds and Seals

  34. Lubrication Systems • Purpose of Oil • oil reduces friction between moving parts • Purpose • lubrication – slippery surface between moving parts • seal – between piston rings and cylinder surface • cool – especially bearings • clean – contaminants held in suspension

  35. Lubrication Systems • Characteristics of Oil • Viscosity and Detergency • viscosity is the oil’s resistance to flow • changes with temperature • SAE numbers: the lower the number, the thinner the oil • Detergency is the oil’s ability to clean • change oil while warm to remove contaminants • Foaming – trapped air bubbles in the oil • reduces lubrication effectiveness • major cause is overfilling of crankcase

  36. Lubrication Systems • Lubrication System of a Typical 4-Cycle Engine

  37. Note Bypass Valve Lubrication Systems • Oil Filters • remove foreign particles from the oil • canister type • replaceable element • full-flow (filters all) and bypass type (filters some) • Caution: do not interchange

  38. Lubrication Systems • Anti-seize Compounds • soft metal particles suspended in grease-like vehicle • reduce the probability of parts rusting together • used on threads, nuts, studs, bolts • Seals • used to seal lubrication on shafts • if leaking, must be replaced

  39. Lubrication Systems • Summary • purpose of oil: lubricate, seal, cool, clean • characteristics: viscosity and detergency • oil filters: remove foreign particles from oil • periodically check oil – don’t overfill • follow manufacturer's recommendations for oil • Change oil and filter • every 100 hours (doesn’t wear out, just gets dirty) • before winter storage

  40. Ignition Systems • Distributor • Condenser and Breaker Points • Other Ignition Systems • Coil • Spark Plug Wire • Spark Plugs

  41. Ignition Systems • Battery and Alternator are Primary Sources of Energy • Ignition Coil Produces High Voltage for Spark Plugs

  42. Ignition Systems • Distributor Delivers Spark to Each Cylinder • at the specific instant when the breaker points open

  43. Ignition Systems • Points and Condenser • old technology • condenser prolongs the life of the points by reducing arcing • breaker points switch the coil’s primary circuit Gap is Adjustable

  44. Ignition Systems • Solid State Ignition • points control a transistor (not full coil current) • increased point life; condenser not required • hotter spark than conventional • can be converted to solid state • Capacitor-Discharge Ignition • variation of transistorized ignition • much hotter spark (hotter than solid state) • Electronic Ignition • replaces points with a control module • individual ignition coil for each spark plug • computer controlled

  45. Electrical and Starting Systems • Boat Batteries • Battery Charging • Starting Systems • Fuses and Circuit Breakers • Wiring

  46. Electrical and Starting Systems • Battery Selection • classification • Starting: provides high current for a short time but is ruined by deep discharges • Deep-Cycle: constructed to tolerate repeated deep discharges – good for use as House batteries • Dual Purpose: provides high starting current and can withstand deep discharges • technologies • Flooded-Cell: regular lead/acid storage battery • Gelled Electrolyte: sealed, maintenance free • Absorbed Glass Mat: glass fiber mats saturated with water-diluted sulfuric acid

  47. Charging Systems • Generators: No Longer in Production • Alternators • driven off engine with vee belt • use diodes to convert AC output to DC for battery charging • will charge batteries, even at low engine rpm

  48. Starting Systems • Electric Starters are Low Voltage, Direct Current Motors Used to Crank the Engine • Starter Components • frame • armature • brushes • field windings • drive mechanism

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

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