1998 EVINRUDE JOHNSON 50HP 2-STROKE OUTBOARD Factory Service & Work Shop Manual

General Informati Tools and Techniq Troubleshooti Lubrication, Maintenance and ~une- I I Synchronization and Linkage Adjustmerits I I I Fuel Systd I Ignition and Electrical System I Power Hea Lower Gearcase and Jet Drive units Trim and Tilt Systerfis I Oil Injection Systems Rope Starters and Remote Controls I I ~ndk I Wiring ~iagra$s I www.manuals-n-more.com.au i General Informatdm Tools and Techniqu~s I TroubleShootirg I Lubrication, Maintenance and Tune-I,Ip I Synchronization and Linkage Adjustments fuel System Ignition and E.lectrical Syste .... s i Power He~d I Lower Gearcase and Jet Drive Un~s Trim and Tilt Systems I Oil Injection Systems Rope Starters and Remote Controls I ! i Index i I Wiring Diagraq..s ! I I

Contents QUICKREFERENCEDATA ................................................ IX CHAPTER ONE ................................................ GENERALINFORMATION 1 Manual organization ............................ 1 Lubricants .................................... 8 Notes. cautions and warnings ..................... 1 Gasket sealant ................................ 10 Torque specifications ............................ 2 Galvanic corrosion ............................. 11 Engine operation ............................... 2 Protection from galvanic corrosion ................ 13 Fasteners ..................................... 2 Propellers .................................... 14 CHAPTER TWO TOOUANDTECHNIQUES ............................................... 21 Safety first ................................... 21 Service hints ................................. 28 Basic hand tools ............................... 21 Special tips ................................... 30 Test equipment ................................ 26 Mechanic's techniques ......................... 31 CHAPTER THREE TROUBLESHOOTING ................................................... 33 Service precautions-1998 model year engines ...... 34 CD2 (capacitor discharge two cylinder) ignition Safety precautions ............................. 34 (4 Deluxe. 6-48 hp. 18jet and 28 jet equipped with Operating requirements ......................... 35 rope start andlor 4 or 5 amp charging system) ...... 93 Test and repair equipment ....................... 36 CD2 (capacitor discharge two cylinder) ignition Wiring harnesses .............................. 42 (40 hp. 50 hp and 35 jet models equipped with Starting system ............................... 43 12 amp regulated charging system) ............. 101 AC (alternating current) lighting coil .............. 62 OIS2000 ignition system Battery charging system ........................ 63 (25 and 35 hp [three-cylinder]models) .......... 108 Electrical accessories ........................... 70 CD3 (capacitor discharge three-cylinder) Warning systems .............................. 70 ignition (50-70 hp models) ................... 117 Ignition system ............................... 78 Fuel system ................................. 130 Indexing flywheel (erratic spark Antisiphon valve tests ......................... 135 [two- and three-cylinder models]) ............... 86 Fuel primer systems ........................... 136 CD1 (capacitor discharge one cylinder) ignition Engine temperature and overheating .............. 139 (2and3.3hpmodels). ........................ 87 Engine ..................................... 145 CD2 (capacitor discharge two-cylinder) ignition (3 and 4 hp [except 4 deluxe] models) ............ 89 CHAPTER FOUR LUBRICATION, MAINTENANCE AND TUNE-UP .............................. 157 Hourmeter .................................. 157 Engine submersion ........................... 177 Fuelsandlubrication .......................... 157 Cooling system flushing ....................... 178 Off-season storage ............................ 172 Tune-up .................................... 181 Anti-corrosion maintenance .................... 176 www.manuals-n-more.com.au Contents QUICK REfERENCE DATA ................................................ IX CHAPTER ONE GENERAL INFORMATION ................................................ 1 ~anualorg~ation ............................ 1 Notes, cautions and warnings . . . . . . . . . . . . . . . . . . . .. 1 Torque specifications. . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 Engine operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 Fasteners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 CHAPTER TWO Lubricants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8 Gasket sealant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10 Galvanic corrosion. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11 Protection from galvanic corrosion. . . . . . . . . . . . . . .. 13 Propellers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14 TOOLS AND TECHNIQUES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 t Safety first . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. 21 Basic hand tools ............................... 21 Test equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26 CHAPTER mREE Service hints ..... . . . . . . . . . . . . . . . . . . . . . . . . . . .. 28 Special tips. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30 ~echanic's techniques ......................... 31 TR.OUBLESHOOTING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 33 Service precautions-1998 model year engines ...... 34 Safety precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34 Operating requirements. . . . . . . . . . . . . . . . . . . . . . . .. 35 Test and repair equipment . . . . . . . . . . . . . . . . . . . . . .. 36 Wiring harnesses. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 42 Starting system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 43 AC (alternating current) lighting coil .............. 62 Battery charging system . . . . . . . . . . . . . . . . . . . . . . .. 63 Electrical accessories. . . . . . . . . . . . . . . . . . . . . . . . . .. 70 Warning systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 70 Ignition system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 78 Indexing flywheel (erratic spark [two- and three-cylinder models]) ............... 86 CDI (capacitor discharge one cylinder) ignition (2 and 3.3 hp models) . . . . . . . . . . . . . . . . . . . . . . . .. 87 CD2 (capacitor discharge two-cylinder) ignition (3 and 4 hp [except 4 deluxe] models) ............ 89 CHAPTER FOUR LUBRICATION, MAINTENANCE AND TUNE-UP Hour meter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 157 Fuels and lubrication. . . . . . . . . . . . . . . . . . . . . . . . .. 157 Off-season storage. . . . . . . . . . . . . . . . . . . . . . . . . . .. 172 Anti-corrosion maintenance. . . . . . . . . . . . . . . . . . .. 176 CD2 (capacitor discharge two cylinder) ignition (4 Deluxe, 6-48 hp, 18 jet and 28 jet equipped with rope start and/or 4 or 5 amp charging system) . . . . .. 93 CD2 (capacitor discharge two cylinder) ignition (40 hp, 50 hp and 35 jet models equipped with 12 amp regulated charging system) . . . . . . . . . . . .. 101 OIS2000 ignition system (25 and 35 hp [three-cylinder] models) . . . . . . . . .. 108 CD3 (capacitor discharge three-cylinder) ignition (50-70 hp models) . . . . .. . . . . . . . . . . . . .. 117 Fuel system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 130 Antisiphon valve tests. . . . . . . . . . . . . . . . . . . . . . . .. 135 Fuel primer systems. . . . . . . . . . . . . . . . . . . . . . . . . .. 136 Engine temperature and overheating. . . . . . . . . . . . .. 139 Engine. . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .. 145 .............................. 157 Engine submersion . . . . . . . . . . . . . . . . . . . . . . . . . .. 177 Cooling system flushing. . . . . . . . . . . . . . . . . . . . . .. 178 Tune-up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 181

CHAPTER FIVE SYNCHRONIZATION AND LINKAGE ADJUSTMENTS ........................... 196 Service precautions-1 998 model year engines ..... 196 6 and 8 hp models ........................... 205 Safety precautions ............................ 196 9.9 and 15 hp models ......................... 208 General information .......................... 197 20-30 hp (two-cylinder) and 18 jet models ......... 212 2and3.3hp ................................. 200 25 and 35 hp (three-cylinder)models ............. 217 3 and 4 hp (except 4 deluxe) .................... 201 40-50 hp (two.cylinder). 28 jet and 35 jet models ... 224 4 Deluxe models ............................. 203 50-70 hp (three-cylinder)models ................ 229 CHAPTER SIX ....................................................... FUELSYSTEM 243 Service precautions-1998 model year engines ..... 243 Fuel primer systems ........................... 279 Fuel system descriptions ....................... 243 Antisiphon protection ......................... 284 Conventional fuel pump service ................. 246 Fuel tanks (integral and portable [remote]) ......... 285 Carburetors ................................. 249 Fuel lines. primer bulbs. fittings and connectors .... 285 Modular carburetor (6-20 hp [two.cylinder]. Fuel filters .................................. 287 25 and 35 hp [three-cylinder] models) ........... 262 Reed valve service ........................... 287 TR and SV carburetors (25 and 30 hp Fuel recirculation systems ...................... 298 [two.cylinder]. 40-70 hp and 18-35jet models) .... 270 CHAPTER SEVEN IGNITION AND ELECTRICAL SYSTEMS ..................................... 305 Service precautions- Capacitor discharge (two-cylinder) ignition 1998 model year engines ..................... 305 (3 and 4 hp models except 4 Deluxe]) .......... 341 Battery ..................................... 305 CD2 (capacitor discharge two cylinder) (4 deluxe, Battery charging system ....................... 3 12 6-48 hp, 18 and 28 jet models with rope start Fuses ...................................... 316 and/or 4 [or 51 amp charging system) ........... 343 Electric starting system ........................ 318 CD2lCD3 (capacitor discharge twolthree cylinder) Neutral safety switch .......................... 329 ignition (40-70 hp and 35 jet models with 12 ................ Flywheel service ............................. 33 1 amp regulated charging system) 348 Ignition systems .............................. 337 OIS2000 ignition system CD1 (capacitor discharge one-cylinder) (25 and 35 hp [three-cylinder]models) .......... 353 ................. ignition (2 and 3.3 hp models) 337 Electrical connector service ..................... 356 CHAPTER EIGHT ....................................................... POWERHEAD 366 Service considerations ......................... 366 Upper crankshaft seal replacement ............ ........... EvinrudeIJohnson model identification 367 (3. 4.30 hp [two-cylinder]and 18jet) 372 Power head break-in .......................... 369 Power head removaVinstallation ................ 373 Service precautions-1998 models ............... 369 Power head disassembly ....................... 392 .............. Service recommendations ...................... 369 Power head cleaning and inspection 422 ......................... Lubricants. sealants and adhesives ............... 370 Power head assembly 436 Sealingsurfaces .............................. 371 Reedvalves ................................. 478 Fasteners and torque .......................... 372 Thermostat .................................. 478 Flywheel ................................... 372 www.manuals-n-more.com.au CHAPTER FIVE. SYNCHRONIZATION AND LINKAGE ADJUSTMENTS. . • • • • • • • • . • • • • . . . • . . • . . • .. t 96 Service precautions-1998 model year engines. . . .. 196 6 and 8 hp models . . . . . . . . . . . . . . . . . . . . . . . . . . .. 205 Safety precautions. . . . . . . . . . . . . . . . . . . . . . . . . . .. 196 9.9 and 15 hp models. . . . . . . . . . . . . . . . . . . . . . . . .. 208 General information. . . . . . . . . . . . . . . . . . . . . . . . . .. 197 20-30 hp (two-cylinder) and 18 jet models. . . . . . . .. 212 2 and 3.3 hp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 200 25 and 35 hp (three-cylinder) models. . . . . . . . . . . .. 217 3 and 4 hp (except 4 deluxe) .................... 201 40-50 hp (two-cylinder), 28 jet and 35 jet models. .. 224 4 Deluxe models ............................. 203 50-70 hp (three-cylinder) models ................ 229 CHAPTER SIX FUEL SYSTEM ........................................................ 243 Service precautions-1998 model year engines ..... 243 Fuel system descriptions. . . . . . . . . . . . . . . . . . . . . .. 243 Conventional fuel pump service . . . . . . . . . . . . . . . .. 246 Carburetors ........ . . . . . . . . . . . . . . . . . . . . . . . .. 249 Modular carburetor (6-20 hp [two-cylinder], 25 and 35 hp [three-cylinder] models) ........... 262 TR and SV carburetors (25 and 30 hp [two-cylinder], 40-70 hp and 18-35 jet models) .... 270 CHAPTER SEVEN Fuel primer systems. . . . . . . . . . . . . . . . . . . . . . . . . .. 279 Antisiphon protection . . . . . . . . . . . . . . . . . . . . . . . .. 284 Fuel tanks (integral and portable [remote]) ......... 285 Fuel lines, primer bulbs, fittings and connectors .... 285 Fuel filters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 287 Reed valve service. . . . . . . . . . . . . . . . . . . . . . . . . . .. 287 Fuel recirculation systems. . . . . . . . . . . . . . . . . . . . .. 298 IGNITION AND ELECTRICAL SYSTEMS •.•••••••••••••••••• 0 • • • • • • • • • • • • • • •• 305 Service precautions- Capacitor discharge (two-cylinder) ignition 1998 model year engines . . . . . . . . . . . . . . . . . . . .. 305 (3 and 4 hp models except 4 Deluxe]) . . . . . . . . . .. 341 Battery ..................................... 305 CD2 (capacitor discharge two cylinder) (4 deluxe, Battery charging system . . . . . . . . . . . . . . . . . . . . . .. 312 6-48 hp, 18 and 28 jet models with rope start Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 316 and/or 4 [or 5] amp charging system). . . . . . . . . . .. 343 Electric starting system ........................ 318 CD2/CD3 (capacitor discharge two/three cylinder) Neutral safety switch .......................... 329 ignition (40-70 hp and 35 jet models with 12 Flywheel service . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 331 amp regulated charging system). . . . . . . . . . . . . . .. 348 Ignition systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 337 OIS2000 ignition system CDI (capacitor discharge one-cylinder) (25 and 35 hp [three-cylinder] models) . . . . . . . . .. 353 ignition (2 and 3.3 hp models) . . . . . . . . . . . . . . . .. 337 Electrical connector service. . . . . . . . . . . . . . . . . . . .. 356 CHAPTER EIGHT PO W£R HEAD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 366 Service considerations. . . . . . . . . . . . . . . . . . . . . . . .. 366 Evinrude/Iohnson model identification ............ 367 Power head break-in .......................... 369 Service precautions-1998 models. . . . . . . . . . . . . .. 369 Service recommendations . . . . . . . . . . . . . . . . . . . . .. 369 Lubricants, sealants and adhesives . . . . . . . . . . . . . .. 370 Sealing surfaces .............................. 371 Fasteners and torque . . . . . . . . . . . . . . . . . . . . . . . . .. 372 Flywheel ................................... 372 Upper crankshaft seal replacement (3,4-30 hp [two-cylinder] and 18 jet) . . . . . . . . . .. 372 Power head removal/installation. . . . . . . . . . . . . . . .. 373 Power head disassembly. . . . . . . . . . . . . . . . . . . . . .. 392 Power head cleaning and inspection. . . . . . . . . . . . .. 422 Power head assembly ....... . . . . . . . . . . . . . . . . .. 436 Reed valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 478 Thermostat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 478

CHAPTER NINE LOWER GEARCASE AND JET DRIVE UNITS . . . . . . . . . . . . .. . . . . . . . . .. . . .. .. . . . Lower gearcase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485 Gearcase disassembly/assembly . . . . . . . . . . . . . . . . . 5 1 Gearcase operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 485 Gearcase cleaning and inspection . . . . . . . . . . . . . . . . 56 4;"' Gear ratio. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487 Gearcase pressure and vacuum tests . . . . . . . . . . . . . . 56 Service precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . 487 Pinion gear shimming (40-70 hp models). . . . . . . . . . 56 Corrosion control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488 Jet drive models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jet pump unit adjustments and maintenance. . . . . . . . 57 1 Shift shaft height adjustment (40-70 hp models) . . . . 569 Gearcase lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . 488 Neutral start adjustment (tiller handle models). . . . . . 489 Propeller.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 Jet pump unit service. . . . . . . . . . . . . . . . . . . . . . . . . . 57 Trim tab adjustment. . . . . . . . . . . . . . . . . . . . . . . . . . . 492 17& Drive shaft and bearing housing . . . . . . . . . . . . . . . . . 58 Gearcase removallinstallation . . . . . . . . . . . . . . . . . . . 492 Water intake housing liner. . . . . . . . . . . . . . . . . . . . . . Water pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504 CHAPTER TEN I TRIM AND TILT SYSTEMS . . . .. . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . .. . .. . . . ~8 Manual tilt assist cylinder . . . . . . . . . . . . . . . . . . . . . . 590 Power trim and tilt system Touch-trimsystem ............................ 592 electrical troubleshooting . . . . . . . . . . . . . . . . . . . . . 6 18 Power trim and tilt systems . . . . . . . . . . . . . . . . . . . . . 595 Electric motor testing . . . . . . . . . . . . . . . . . . . . . . . . . 62k Power trim and tilt hydraulic troubleshooting. . . . . . . 607 Power trim and tilt system service . . . . . . . . . . . . . . . CHAPTER ELEVEN OIL INJECTION SYSTEMS. . . . . . . . .. .. . . . . .. . . . . . .. . . . . .. . .. . . . . . . . . . . . .. 461 Service precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 1 VRO oil injection (35 jet, 40 hp [electric start] and 50-70 hp models). . . . . . . . . . . . . . . . . . . . . . . . 1 Accumix R oil injection system . . . . . . . . . . . . . . . . . 662 Constant ratio oil injection (25 and 35 hp [three-cylinder]). . . . . . . . . . . . . . . . . 665 CHAPTER TWELVE 1 ROPE STARTERS AND REMOTE CONTROLS. . . . . . . . . . . . . . . . . . . . .. ... ... . . . . . q93 Rope (manual) starters. . . . . . . . . . . . . . . . . . . . . . . . . 693 Remote controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 716 INDEX ............................................................. T5 WIRINGDIAGWS .................................................. 'r www.manuals-n-more.com.au CHAPTER NINE LOWER GEARCASE AND JET DRIVE UNITS Lower gearcase . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 485 Gearcase operation ........................... 485 Gear ratio. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 487 Service precautions . . . . . . . . . . . . . . . . . . . . . . . . . .. 487 Corrosion control. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 488 Gearcase lubrication . . . . . . . . . . . . . . . . . . . . . . . . .. 488 Neutral start adjustment (tiller handle models) ...... 489 Propeller .................................... 489 Gearcase disassembly/assembly ................ . Gearcase cleaning and inspection ............... . Gearcase pressure and vacuum tests ............. . Pinion gear shimming (40-70 hp models) ......... . Shift shaft height adjustment (40-70 hp models) ... . Jet drive models ............................. . Jet pump unit adjustments and maintenance ....... . Jet pump unit service ......................... . 1 85 ;~e~ 56 56 569 57b~ 57 57 Trim tab adjustment. . . . . . . . . . . . . . . . . . . . . . . . . .. 492 Gearcase removal/installation. . . . . . . . . . . . . . . . . .. 492 Water pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 504 Drive shaft and bearing housing. . . . . . . . . . . . . . . .. 58 Water intake housing liner. . . . . . . . . . . . . . . . . . . . .. 58, CHAPTER TEN TRIM AND TILT SYSTEMS Manual tilt assist cylinder. . . . . . . . . . . . . . . . . . . . .. 590 Touch-trim system. . . . . . . . . . . . . . . . . . . . . . . . . . .. 592 Power trim and tilt systems. . . . . . . . . . . . . . . . . . . .. 595 Power trim and tilt hydraulic troubleshooting. . . . . .. 607 CHAPTER ELEVEN Power trim and tilt system electrical troubleshooting .................... . Electric motor testing ........................ . Power trim and tilt system service .............. . OIL IN)ECnON SYSTEMS ...• .... •• ...... ••.•...••..•...• ........... •... Service precautions ........................... 661 VR0 2 oil injection (35 jet, 40 hp [electric start] Accumix R oil injection system ................. 662 and 50-70 hp models) ....................... . Constant ratio oil injection (25 and 35 hp [three-cylinder]) ................. 665 CHAPTER TWELVE ROPE STARTERS AND REMOTE CONTROLS ..•...•.• ........... ••...••• ..... Rope (manual) starters ......................... 693 Remote controls ............................. . INDEX ............................................................ . WIRING DIAGRAMS ................................................. . 66. I 67B I q93 7lfu J 25 28

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Chapter One General Information This detailed, comprehensive manual contains complete information covering maintenance, repair and overhaul. Hundreds of photos and drawings guide you throughout every procedure. Troubleshooting, tune-up, maintenance and repair are not d~fficul if you know what tools and equipment to use and what to do. Anyone not afiaid to get their hands dirty, of average in- telligence and with some mechanical ability can perform most of the procedures in this manual. See Chapter Two for more information on tools and techniques. A shop manual is a reference. You want to be able to find information quickly. Clymer books are designed with you in mind. All chapters are thumb tabbed and important items are indexed at the end of the manual. All procedures, tables, photos and instructions in this manual assume the reader may be worlung on the machine or using the manual for the first time. Keep the manual in a handy place in your tool- box or boat. It will help you to better understand how your boat runs, lower repair and maintenance costs and generally increase your enjoyment of your boat. MANUAL ORGANIZATION This chapter provides general information useful to boat owners and marine mechanics. Chapter Two discusses the tools and techniques for preventative maintenance, troubleshooting and repair. Chapter Three provides troubleshooting and testing procedures for all systems and individual components. Following chapters describe specific systems, providing disassembly, inspection, assembly and adjustment procedures in simple step-by- step form. Specifications concerning a specific system are included at the end of the appropriate chapter. www.manuals-n-more.com.au Chapter One General Information This detailed, comprehensive manual contains complete information covering maintenance, repair and overhaul. Hundreds of photos and drawings guide you throughout every procedure. Troubleshooting, tune-up, maintenance and repair are not difficult if you know what tools and equipment to use and what to do. Anyone not afraid to get their hands dirty, of average in- telligence and with some mechanical ability can perform most of the procedures in this manual. See Chapter Two for more information on tools and techniques. A shop manual is a reference. You want to be able to fmd information quickly. Clymer books are designed with you in mind. All chapters are thumb tabbed and important items are indexed at the end of the manual. All procedures, tables, photos and instructions in this manual assume the reader may be working on the machine or using the manual for the fIrst time. Keep the manual in a handy place in your tool- box or boat. It will help you to better understand how your boat runs, lower repair and maintenance costs and generally increase your enjoyment of your boat. MANUAL ORGANIZATION This chapter provides general information useful to boat owners and marine mechanics. Chapter Two discusses the tools and techniques for preventative maintenance, troubleshooting and repair. Chapter Three provides troubleshooting and testing procedures for all systems and individual components. Following chapters describe specifIc systems, providing disassembly, inspection, assembly and adjustment procedures in simple step-by- step form. Specifications concerning a specific system are included at the end of the appropriate chapter.

CHAPTER ONE NOTES, CAUTIONS AND WARNINGS The terms NOTE, CAUTION and WARNING have specific meanings in this manual. A NOTE provides additional information to make a step or procedure easier or more clear. Disregarding a NOTE could cause inconvenience, but would not cause damage or personal injury. A CAUTION emphasizes areas where equipment damage could cause permanent mechanical damage; however, personal injury is unlikely. A WARNING emphasizes areas where personal injury or even death could result from neg- ligence. Mechanical damage may also occur. WARNINGS must be taken seriously. In some cases, serious injury or death has resulted from disregarding similar warnings. TORQUE SPECIFICATIONS Torque specifications throughout this manual are given in foot-pounds (ft.-lb.), inch-pounds (in.-lb.) and newton meters (N-m.). Newton meters are being adopted in place of meter-kilograms (mkg) in accordance with the International Modernized Metric System. Ex- isting torque wrenches calibrated in meter-lulograms can be used by performing a simple conversion: move the decimal point one place to the right. For example, 4.7 mkg = 47 N-m. This conversion is accurate enough for most mechanical operations even though the ex- act mathematical conversion is 3.5 mkg = 34.3 N-m. ENGINE OPERATION All marine engines, whether two or four-stroke, gasoline or diesel, operate on the Otto cycle of intake, compression, power and exhaust phases. Wo-Stroke Cycle A two-stroke engine requires one crankshaft revolution (two strokes of the piston) to complete the Otto cycle. All engines covered in this manual are a two-stroke design. Figure 1 shows gasoline two-stroke engine operation. Four-Stroke Cycle A four-stroke engine requires two crankshaft revolutions (four strokes of the piston) to complete the Otto cycle. Figure 2 shows gasoline four-stroke engine operation. FASTENERS The material and design of the various fasteners used on marine equipment are carefully thought out and designed. Fastener design deter- mines the type of tool required to work with the fastener. Fastener material is carefully selected to decrease the possibility of physical failure or corrosion. See Galvanic Corrosion in this chapter for information on marine materials. Nuts, bolts and screws are manufactured in a wide range of thread patterns. To join a nut and bolt, the diameter of the bolt and the diameter of the hole in the nut must be the same. It is just as important that the threads are compatible. The easiest way to determine if fastenef threads are compatible is to turn the nut on the bolt, or bolt into its threaded opening, using fid- gers only. Be sure both pieces are clean. If much force is required, check the thread condition o t each fastener. If the thread condition is good byt the fasteners jam, the threads are not cornpati; ble. I I Four important specifications describe the thread: 1 1. Diameter. I I 2. Threads per inch. I I 3. Thread pattern. 1 www.manuals-n-more.com.au 2 NOTES, CAUTIONS AND WARNINGS The terms NOTE, CAUTION and WARNING have specific meanings in this manual. A NOTE provides additional information to make a step or procedure easier or more clear. Disregarding a NOTE could cause inconvenience, but would not cause damage or personal injury. A CAUTION emphasizes areas where equipment damage could cause permanent mechanical damage; however, personal injury is unlikely. A WARNING emphasizes areas where personal injury or even death could result from neg- ligence. Mechanical damage may also occur. WARNINGS must be taken seriously. In some cases, serious injury or death has resulted from disregarding similar warnings. TORQUE SPECIFICATIONS Torque specifications throughout this manual are given in foot-pounds (ft.-lb.), inch-pounds (in.-lb.) and newton meters (Nem.). Newton meters are being adopted in place of meter-kilograms (mkg) in accordance with the International Modernized Metric System. Ex- isting torque wrenches calibrated in meter-kilograms can be used by performing a simple conversion: move the decimal point one place to the right. For example, 4.7 mkg = 47 N em. This conversion is accurate enough for most mechanical operations even though the ex- act matr~ematical conversion is 3.5 mkg = 34.3 Nem. ENGINE OPERATION All marine engines, whether two or four-stroke, gasoline or diesel, operate on the Otto cycle of intake, compression, power and exhaust phases. CHAPTER ONE Two-Stroke Cycle A two-stroke engine requires one crankshaft revolution (two strokes of the piston) to complete the Otto cycle. All engines covered in thiis manual are a two-stroke design. Figure 1 s~ows gasoline two-stroke engine operation. Four-Stroke Cycle A four-stroke engine requires two crankshaft revolutions (four strokes of the piston) to complete the Otto cycle. Figure 2 shows gasoline four-stroke engine operation. FASTENERS The material and design of the various fasteners used on marine equipment are carefully thought out and designed. Fastener design deter- mines the type of tool required to work with the fastener. Fastener material is carefully selected to decrease the possibility of physical failure or corrosion. See Galvanic Corrosion in this chapter for information on marine materials. Nuts, bolts and screws are manufactured in a wide range of thread patterns. To join a nut an~ bolt, the diameter of the bolt and the diameter Qf the hole in the nut must be the same. It is just a:s important that the threads are compatible. The easiest way to determine if fastener threads are compatible is to turn the nut on thr bolt, or bolt into its threaded opening, using finj- gers only. Be sure both pieces are clean. If muc~ force is required, check the thread condition Of each fastener. If the thread condition is good h9t the fasteners jam, the threads are not compat~- I bk. I Four important specifications describe thf thread: I 1. Diameter. I 2. Threads per inch. 3. Thread pattern.

GENERAL INFORMATION 3 0 TWO-STROKE OPERATING PRINCIPLES I AS the piston travels down- I ward, it uncovers the exhaust port (A) allowing the exhaust gases to leave the cylinder. A fresh air-fuel charge, which has been compressed slightly in the crankcase, enters the cylinder throughsthe transfer port (B). Since this charge enters under pressure, it also helps to push out the exhaust gases. As the piston almost reaches the top of the travel, the spark plug fires, igniting the compressed air-fuel mixture. The piston continues to top dead center (TDC) and is pushed downward by the expanding gases. While the crankshaft continues to rotate, the piston moves upward, covering the transfer (B) and exhaust (A) ports. The piston compresses the new air-fuel mixture and creates a low-pressure area in the crancase at the same time. As the piston continues to travel, it uncovers the intake port (C). A fresh air-fuel charge from the carburetor (D) As the piston travels down, the exhaust gases leave the = - I cylinder and the complete cy- = - - cle starts all over again. www.manuals-n-more.com.au GENERAL INFORMATION TWO·STROKE OPERATING PRINCIPLES As the piston travels downward, it uncovers the exhaust port (A) allowing the exhaust gases to leave the cylinder. A fresh air-fuel charge, which has been compressed slightly In the crankcase, enters the cylinder through the transfer port (8). Since this charge enters under pressure, It also helps to push out the exhaust gases. As the piston almost reaches the top of the travel, the spark plug fires, igniting the compressed air-fuel mixture. The piston continues to top dead center (TDC) and Is pushed downward by the expanding gases. 1 3 B While the crankshaft continues to rotate, the piston moves upward, covering the transfer (8) and exhaust (A) ports. The piston compresses the new air-fuel mixture and creates a low-pressure area in the crancase at the same time. As the piston continues to travel, It uncovers the intake port (e). A fresh air-fuel charge from the carburetor (D) is drawn Into the crankcase through the Intake port. As the piston travels down, the exhaust gases leave the cylinder and the complete cycle starts all over again. 3

1998 EVINRUDE JOHNSON 50HP 2-STROKE OUTBOARD Factory Service & Work Shop Manual

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