TOHATSU OUTBOARD 25HP 50HP Engine Shop Manual

General Information Tools and Techniques Troubleshooting and Testing Lubrication, Maintenance and Tune-Up Synchronization and Adjustment Fuel System Electrical and Ignition Systems Power Head Gearcase and Midsection Manual Rewind Starter Power Trim and Tilt Repair Index Wiring Diagrams

Contents CHAPTER ONE GENERALlNFORMATION. ............................. 1 ................................. Manual organization ........................ 1 Lubricants 8 .............................. Notes. cautions and warnings ................. 1 Gasket sealant I0 .......................... Torque specifications ....................... 2 Galvanic corrosion I I .............. Engine operation ........................... 2 Protection from galvanic corrosion 13 ................................. Fasteners ................................. 2 Propellers 14 CHAPTER TWO ........................................... TOOLS AND TECHNIQUES 21 ............................... Safety first ................................ 21 Service hints 28 ................................ Basic hand tools ............................ 21 Special tips 30 ....................... Test equipment ............................ 26 Mechanics' techniques 31 CHAPTER THREE TROUBLESHOOTING AND TESTING* ............................. Test equipment 33 Troubleshooting preparation ................... 36 Operating requirements ...................... 37 Starting difficulty .......................... 37 Ignition system testing ...................... 39 Warning system ............................ 44 Starting system ............................ 45 Charging system ........................... 50 Fuses and wire harness ....................... 54 Engine speed limiting system .................. 54 ................................ Trim system 57 ............................ Electrical testing 63 .............................. Engine noises 67 ............................. Cooling system 69 .................................. Gearcase 72

CHAPTER FOUR LUBRICATl0N.IWAINTENANCEANDTUNE~UP ............................ 80 Tune-up .................................. 92 Storage ................................... 97 Submersion ............................... 96 CHAPTER FIVE SYNCHRONIZATION AND ADJUSTMENT* 101 ......... Fuel system ................................ 101 Throttle linkage adjustment (all models) 115 Ignition timing ............................ 106 CHAPTER SIX FUELSYSTEM .................................................... 126 ................................ Fuelta nk .................................. 129 Fuelpumps 133 ................................. Fuel filter replacement ....................... 132 Carburetor 137 Primer bulb ............................... 132 CHAPTER SEVEN ELECTRICAL AND IGNITION SYSTEMS 149 Battery .................................. 149 Charging system ............................ 163 Electric starting system ....................... 154 Ignition system ............................. 165 ............................. Starter motor .............................. 154 Warning system 171 CHAPTER EIGHT POWERHEAD .................................................... 181 ................................. Flywheel .................................. 181 Inspection 202 Powerhead ................................ 186 CHAPTER NINE GEARCASEANDMIDSECTION ....................................... 213 ................................ Gearcase operation .......................... 213 Water pump 222 .................................. Propeller removal and installation .............. 214 Gearcase 228 .............. ................................. Gearcase removal and installation 2 16 Inspection 252 CHAPTER TEN ......................................... MANUALREWINDSTARTER 257 ................ Removal. repair and installation 257

CHAPTER ELEVEN POWER TRIM AND TILT REPAIR ...................................... 263 Fluid filling ................................ 269 Air bleeding ............................... 269 WIRING DlAGRAlMS ............................................... 282

Chapter One General Informi\tion This detailed, comprehensive manual con- tains complete information on maintenance, tune-up, repair and overhaul. Hundreds of photos and drawings guide you through every step- by-step 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 intelligence and with some mechanical ability, can perform most of the procedures in this book. See Chapter Two for more information on tools and techniques. A shop manual is a reference. You want to be able to find information fast. These books are designed with you in mind. All chapters are thumb tabbed and important items are indexed at the end of the book. All procedures, tables, photos, etc., in this manual assume that the reader may be working on the machine or using this manual for the first time. Keep this book handy in your tool box. It will help you to better understand how your machine runs, lower repair and maintenance costs and generally increase your enjoyment of your marine equipment. MANUAL ORGANIZATION This chapter provides general information useful to marine owners and mechanics. Chapter Two discusses the tools and techniques for preventive maintenance, troubleshooting and repair. Chapter Three describes typical equipment problems and provides logical troubleshooting procedures. Following chapters describe specific systems, providing disassembly, repair, assembly and adjustment procedures in simple step- by- step form. Specifications concerning a specific system are included at the end of the appropriate chapter. NOTES, CAUTIONS AND WARNINGS The terms NOTE, CAUTION and WARN- ING have specific meanings in this manual. A NOTE provides additional information to make a step or procedure easier or clearer. Disregard- ing a NOTE could cause inconvenience, but would not cause damage or personal injury.

CHAPTER ONE A CAUTION emphasizes areas where equipment damage could result. Disregarding a CAU- TION could cause permanent mechanical damage; however, personal injury is unlikely. A WARNING emphasizes areas where personal injury or even death could result from negligence. Mechanical damage may also occur. WARNINGS are to 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.) and either New- ton meters (N.m) or meter-kilograms (rnkg). Newton meters are being adopted in place of meter-kilograms in accordance with the Interna- tional Modernized Metric System. Existing 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.m. This conversion is accurate enough for mechanics' use even though the exact mathematical conversion is 3.5 mkg = 34.3 N.m. ENGINE OPERATION All marine engines, whether 2- or 4-stroke, gasoline or diesel, operate on the Otto cycle of intake, compression, power and exhaust phases. 4-stroke Cycle A 4-stroke engine requires two crankshaft revolutions (4 strokes of the piston) to complete the Otto cycle. Figure 1 shows gasoline 4-stroke engine operation. Figure 2 shows diesel 4-stroke engine operation. 2-stroke Cycle A 2-stroke engine requires only 1 crankshaft revolution (2 strokes of the piston) to complete the Otto cycle. Figure 3 shows gasoline 2-stroke engine operation. Although diesel 2-strokes ex- ist, they are not commonly used in light marine applications. FASTENERS The material and design of the various fasteners used on marine equipment are not arrived at by chance or accident. 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 corsosion. See Galvanic Corrosio~ in this chapter for more information on marine materials. Threads 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 impoflant that the threads on both be properly matched. The best way to determine if the threads on two fasteners are matched is to turn the nut on the bolt (or the bolt into the threaded hole in a piece of equipment) with fingers only. Be sure both pieces are clean. If much force is required, check the thread condition on each fastener. If the thread condition is good but the fasteners jam, the threads are not compatible. Four important specifications describe every thread: a. Diameter. b. Threads per inch. c. Thread pattern. d. Thread direction. Figure 4 shows the first two specifications. Thread pattern is more subtle. Italian and British

TOHATSU OUTBOARD 25HP 50HP Engine Shop Manual

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