1983 Mercury 50HP 4 Cyl 2-Stroke Outboard Service & Repair Manual

ENGINE FINDER The following listings contain all engines covered in this manual Model/Engine Year 45 hp, 4 cyl ...................... 1965 - 1970 50 hp, 3 cyl ...................... 1986 - 1989 500/50 hp, 4 cyl ................... 1965 - 1985 60 hp, 3 cyl ...................... 1984 - 1989 650/65 hp, 3 cyl ................... 1972 - 1976 650/65 hp, 4 cyl ................... 1965 - 1971 650,700/70 hp, 3 cyl ............... 1976 - 1983 70 hp, 3 cyl ...................... 1986 - 1989 75 hp, 4 cyl ...................... 1984 - 1986 80 hp, 3 cyl ...................... 1987 - 1989 800/80 hp, 4 cyl ................... 1969 - 1983 850/85 hp, 4 cyl ................... 1973 - 1977 90 hp, 3 cyl ...................... 1987 - 1989 850XS/90 hp, 4 cyl ...................... 1976 100 hp, 4 cyl ..................... 1988 - 1989 115 hp, 4 cyl ..................... 1988 - 1989

TABLE OF CONTENTS 1 SAFETY INTRODUCTION 1-1 CLEANING, WAXING, & POLISHING 1-1 CONTROLLING CORROSION 1-1 PROPELLERS 1-2 FUEL SYSTEM 1-7 LOADING 1-9 HORSEPOWER 1-10 FLOTATION 1-10 EMERGENCY EQUIPMENT 1-12 COMPASS 1-14 ANCHORS 1-16 MISCELLANEOUS EQUIPMENT 1-17 BOATING ACCIDENT REPORTS 1-18 NAVIGA TION 1-18 2 TUNING INTRODUCTION 2-1 TUNE-UP SEQUENCE 2-2 COMPRESSION CHECK 2-3 SPARK PLUG INSPECTION 2-3 IGNITION SYSTEM 2-4 TIMING AND SYNCHRONIZING 2-5 CARBURETOR ADJUSTMENT 2-7 FUEL PUMPS 2-9 CRANKING MOTOR AND SOLENOID 2-10 INTERNAL WIRING HARNESS 2-11 WATER PUMP CHECK 2-12 PROPELLER 2-13 LOWER UNIT 2-15 BOAT TESTING 2-16 3 POWERHEAD INTRODUCTION 3-1 Chapter Organization 3-3 POWERHEAD SERVICE -- ORIGINAL DESIGN (See Listing on Page) 3-5 Removal 3-5 Disassembling 3-7 Cleaning & Inspecting 3-66 Assembling 3-14 Installation 3-25 POWERHEAD SERVICE -- REDESIGNED MODEL (See Listing on Page) 3-27 Removal 3-27 Disassembling 3-32 Cleaning & Inspecting 3-66 Assembling 3-48 Installation 3-60 CLEANING & INSPECTING 3-66 Thermostat Service 3-66 Reed Block Service 3-66 Crankshaft Service 3-68 Connecting Rod Service 3-70 Piston Service 3-72 Honing Procedures 3-74 Cylinder Block Service 3-75 Check valves 3-76 4 FUEL INTRODUCTION GENERAL CARBURETION INFORMA TION TROUBLESHOOTING "Sour" Fuel Leaded Gasoline & Gasohol Removing Fuel From the System Fuel Pump Test Fuel Line Test Rough Engine Idle Excessive Fuel Consumption' Engine Surge Anti-Syphon Valve ENRICHENER SYSTEM 2+2 SYSTEM W/ACCELERATOR PUMP -- 100 & 115HP CARBURETOR IDENTIFICATION REFERENCED "A" - SIDE BOWL AND BACK DRAG Removal & Disassembling Cleaning & Inspecting Assembling Installation Adjustments 4-1 4-1 4-4 4-4 4-5 4-5 4-7 4-9 4-10 4-10 4-11 4-11 4-11 4-12 4-13 4-14 4-14 4-16 4-19 4-21 4-23

4 FUEL (Continued) Cleanin~ &: Inspecting 5-14 REFERENCED "B" W/INTEGRAL Assemb ing 5-17 TYPEII-THUNDERBOLT- FUEL PUMP 4-24 DISTRIBUTOR LIGHTNING Removal &: Disassembling 4-24 ENERGIZER - POINTLESS Cleaning &: Inspecting 4-26 AKA ALTERNATOR DRIVER Assembling 4-27 IGNITION (ADI) 5-23 Installation 4-29 Description 5-23 Adjustments 4-30 Troubleshooting 5-23 REFERENCED "C" - CENTER Removal 5-26 SQUARE BOWL 4-31 Cleaning &: Inspecting 5-28 Removal &: Disassembling 4-31 Assembling 5-28 Cleaning &: Inspecting 4-34 Installa tion 5-29 Assembling 4-36 TYPEIIT-THUNDERBOLT- Installation 4-38 DISTRIB UTOR C.D. - Operating Adjustments 4-39 POINTLESS 5-31 REFEREN CED "D" SERIES W ME Description 5-31 CENTER SQUARE BOWL 4-41 Troubleshooting 5-33 Removal &: Disassembling 4-41 Servicing 5-34 Cleaning &: Inspecting 4-43 Removal 5-37 Assembling 4-45 Cleaning &: Inspecting 5-38 Installation 4-46 Assembling 5-38 Adj ustm ents 4-47 TYPEIV-THUNDERBOLT- FUEL PUMP 4-47 FL YWHEEL - C.D. - POINTLESS 5-40 Theory of Operation 4-47 Description &: Operation 5-40 Pump Pressure Check 4-49 Troubleshooting 5-41 Removal 4-50 Servicing 5-43 Cleaning &: Inspecting 4-51 Removal 5-43 Assembling 4-51 Installa tion 5-44 OIL INJECTION -- AUTO BLEND 4-53 TYPE V - THUNDERBOLT - Description 4-53 FL YWHEEL - C.D. - Troubleshooting 4-55 COIL PER CYLINDER 5-45 Preparation for Use Description &: Operation 5-45 Auto Blend 4-58 Troubleshooting 5-46 OIL INJECTION -- ADVANCED 4-59 Servicing 5-54 Description 4-59 Removal &: Disassembling 5-54 Filling System 4-60 Cleaning &: Inspecting 5-56 Purging System 4-61 Assembling &: Installation 5-57 Troubleshooting 4-61 Servicing System 4-63 6 nMING AND SYNCHRONIZING Disassembling 4-64 INTRODUCTION &: PREP ARA TION 6-1 Cleaning &: Inspecting 4-65 Assembling 4-67 MODEL 500 1965-1967 and Installation 4-69 1968 to Ser ial No. 2306755 6-3 MODEL 500S No. 2306756 and Up 5 IGNInON Mid 1968 MODEL 500M No. 2307056 and Up INTRODUCTION 5-1 Mid 1968 SPARK PLUG EVAUJA TION 5-2 MODEL 500E No. 2406035 and Up POLARITY CHECK 5-4 Mid 1968 to 1975 WIRING HARNESS 5-5 MODEL 650S No. 2312311 to 2446775 TYPE I - DISTRIBUTOR MAGNETO Mid 1968 and 1969 WITH POINTS 5-6 MODEL 650E No. 2446775 to 2606853 Description &: Operation 5-6 Mid 1968 and 1969 6-4 Troubleshooting 5-8 MODEL 500 1975 6-7 Servicing 5-12 MODEL 500 1976 to No. 4576236 6-10

MODEL 500 No. 4576237 and Up STA TOR SERVICE 7-17 1977 to 1979 Removal 7-18 MODEL 50HP Since 1979 Installation 7-18 MODEL 45HP 1986 to 1989 CHOKE CIRCUIT AND MODEL 40HP Since 1990 6-11 ENRICHENER SYSTEM 7-19 CRANKING MOTOR CIRCUIT 7-20 MODEL 650 1965 and 1966 Description & Oper ation 7-20 MODEL 650E 1968 to No. 2446744 Troubleshooting 7-21 MODEL 650S 1968 to No. 2312310 6-13 Removal 7-25 Disassembling - Pinion Gear MODEL 650 1970 and 1971 with Rubber Cushion 7-26 MODEL 800 1969 to 1972 Assembling 7-26 MODEL 850 1973 6-15 Disassembling - Pinion Gear with Snap Ring or Nut 7-27 MODEL 650 1972 to 1975 6-17 Assembling 7-28 MODEL 650 1976 6-19 Disassembling - Pinion Gear wi th Top Spring 7-29 MODEL 700 1977 to 1979 Assembling 7-30 MODEL 70HP 1979 to 1983 CRANKING MOTOR REPAIR 7-30 MODEL 60HP 1984 to 1990 Disassembling 7-31 MODEL 50HP 1986 to 1990 6-21 Testing Parts 7-32 Cleaning & Inspecting 7-34 MODEL 850 1974 and 1975 Assembling a Bosch 7-39 To No. 4366801 6-23 Assembling a Delco Remy 7-39 MODEL 800 1978 and 1979 MODEL 850 1976 and 1977 8 REMOTE CONTROLS No. 4366802 and Above MODEL 80HP 1979 to 1983 INTRODUCTION 8-1 MODEL 75HP 1984 to 86 6-25 STEERING SYSTEMS 8-1 DIRECTIONAL INDICA TOR 8-2 MODEL 90HP Since 1987 ROTAR Y STEERING SERVICE 8-5 MODEL 70HP, & 80HP 1987 to 1989 Disassembling 8-5 MODEL 75HP Since 1990 Cleaning & Inspecting 8-5 MODEL 50HP Since 1991 Assembling 8-6 MODEL 60HP Since 1991 6-27 STANDARD RIDE GUIDE KIT 8-8 MODEL 100HP Since 1988 CUSTOM RIDE GUIDE KIT 8-8 ALSO MODEL 115HP Since 1989 6-29 MERCONTROL PANEL EARLY MODEL 8-8 Disassembling 8-8 7 ELECTRICAL Assembling 8-11 MERCONTROL BOX LATE MODEL 8-13 INTRODUCTION 7-1 Disassembling 8-13 BATTERIES 7-1 Assembling 8-16 GA UGES AND HORNS 7-7 COMMANDER CONTROL BOX Temperature Gauges 7-8 Removal & Disassembling 8-17 Warning Lights 7-8 Cleaning & Inspecting 8-24 Fuel Gauges 7-9 Assembling & Installation 8-26 Tachometer 7-11 CABLE ADJUSTMENTS 8-35 Horns 7-11 ELECTRICAL SYSTEM 7-12 General Information 7-12 9 POWER TRIM/TILT CHARGING CIRCUIT SERVICE 7-13 Troubleshooting 7-14 INTRODUCTION 9-1 Rectifier Removal 7-15 Chapter Organization 9-2 Rectif ier Installation 7-17 MECHANICAL TILT PIN 9-2

9 POWER TRIM/TILT (Continued) Disassembling Bear ing Carr ier 10-16 SYSTEM "A" - MODELS WITH TWO Propeller Shaft 10-17 TRIM/TIL T CYLINDERS 9-3 Driveshaft 10-17 Description &: Operation 9-3 Special Instructions 9-5 Assembling Bleeding 9-6 Lower Driveshaft Bearing 10-22 Troubleshooting 9-8 Shift Shaft 10-22 Trim Switch Service 9-8 Bearing Carrier 10-23 Service System "A" 9-12 Forward Gear &: Bearing 10-24 Hydraulic Pump Service 9-14 Forward Bearing Race 10-25 Electric Motor Service 9-17 Driveshaft 10-26 Shimming &: Backlash SYSTEM "B" - MODELS WITH TWO Pinion Gear Depth 10-28 TRIM CYLINDERS Forward Gear Backlash 10-29 AND ONE TILT CYLINDER 9-21 Assembling &: Installation Description &: Operation 9-21 Bear ing Carr ier 10-32 Bleeding 9-22 Reverse Gear Backlash '10-33 Flushing 9-23 Troubleshooting 9-24 SERVICING CAM-SHIFT TYPE II Removal &: Disassembling 9-31 UNITS MATCHED WITH LATE Manual Release Valve 9-34 3- and 4-CYLINDER POWERHEADS Oil Reservoir Cover 9-35 SINCE ABOUT 1980 10-34 Trim Cylinders 9-35 Removal and Disassembling Tilt Cylinder 9-36 Bearing Carr ier 10-35 Motor &: Pump 9-36 Propeller Shaft 10-36 Cleaning &: Inspecting 9-37 Shift Shaft 10'-37 Assembling &: Installation 9-38 Pinion Gear 10-38 Pump &: Motor 9-42 Driveshaft 10-38 Tilt Cylinder 9-45 Forward Gear 10-39 Trim Cylinders 9-48 Pinion Gear Bearing Race 10-40 Reservoir Cover 9-49 Forward Bearing Race 10-40 Manual Release Valve 9-49 Driveshaft Bearing 10-40 System Installation 9-50 Assembling and Installation Driveshaft Bear ing 10-41 10 LOWER UNIT Pinion Gear Bearing Race 10-44 Forward Gear Bearing Race 10-44 DESCRIPTION 10-1 Shift Shaft 10-45 CHAPTER COVERAGE 10-1 Forward Gear 10-45 TROUBLESHOOTING 10-4 Driveshaft 10-46 REMOV AL -- ALL UNITS 10-5 Pinion Gear 10-46 Propeller Shaft 10-47 Propeller Removal 10-7 Bear ing Carr ier 10-48 WATER PUMP SERVICE Pinion Gear Depth 10-49 Removal and Disassembling Forward Gear Backlash 10-50 High Pressure Type Pump 10-8 WATER PUMP ASSEMBLING AND High Volume Type Pump 10-9 INSTALLA TION High Pressure Type Pump 10-52 SERVICING CAM-SHIFT TYPE I Shimming (Certain Units) 10-52 UNITS MATCHED WITH EARLY High Volume Type Pump 10-56 3-CYLINDER POWERHEADS CLEANING AND INSPECTING TO ABOUT 1979 10-11 ALL UNITS 10-57 Removal Bear ing Carr ier and LOWER UNIT INSTALLATION 10-60 Propeller Shaft 10-12 Filling Lower Unit 10-60 Driveshaft &: Bearing 10-13 Exhaust Tube Installation 10-61 Forward Gear &: Bear ing 10-15 Propeller Installation 10-64

11 HAND REWIND STARTER PROPELLER SERVICE 12-13 POWER TRIM/TILT 12-15 INTRODUCTION INSIDE THE BOAT 12-16 TYPE "A" (See Introduction) 11-2 LOWER UNIT 12-16 Removal and Disassembling 11-2 WINTER STORAGE 12-18 Cleaning and Inspecting 11-4 Units With Oil Injection 12-19 Assembling and Installation 11-6 Battery Storage 12-20 Type ''S" (See Introduction) APPENDIX Removal and Disassembling 11-13 Cleaning and Inspecting 11-16 METRIC CONVERSION CHART A-I Assembling and Installation 11-17 ENGINE SPECIFICATIONS AND TUNE-UP ADJ. A-2 thru A-12 12 MAINTENANCE REED STOP OPENING A-13 INTRODUCTION 12-1 CARBURETORJETS~E/ ELEV ATION CHART A-14 OUTBOARD SERIAL NUMBERS 12-2 LOWER UNIT BACKLASH TABLE A-16 LUBRICA TION - COMPLETE UNIT 12-2 LOWER UNIT OIL CAPACITY PRE-SEASON PREP ARA TION 12-3 AND GEAR CHART A-17 Units With Oil Injection 12-4 PISTON & CYLINDER All Units 12-5 SPECIFICA TIONS A-18 FIBERGLASS HULLS 12-10 WIRE IDENTIFICATION DWGS. BELOW WATERLINE SERVICE 12-10 Igni tion Systems A-19 thru A-39 SUBMERGED ENGINE SERVICE 12-11 Power Trim/Til t A-40 Salt Water Submersion 12-11 Remote Controls A-43 Fresh Water Submersion 12-12 Console Wiring A-47

1 SAFETY 1-1 INTRODUCTION In order to protect the investment for the boat and outboard, they must be cared for properly while being used and when out of the water. Always store the boat with the bow higher than the stern and be sure to remove the transom drain plug and the inner hull drain plugs. If any type of cover is used to protect the boat, be sure to allow for some movement of air through the hull. Proper ventilation will assure evaporation of any condensation that may form due to changes in temperature and humidity. 1-2 CLEANING, WAXING, AND POLISHING Any boat should be washed with clear water after each use to remove surface dirt and any salt deposits from use in salt water. Regular rinsing will extend the time be- tween waxing and polishing. It will also give you "pride of ownership", by having a sharp looking piece of equipment. Elbow grease, a mild detergent, and a brush will be required' to remove stubborn dirt, oil, and other un- sightly deposits. Stay away from harsh abrasives or strong chemical cleaners. A white buffing com- pound can be used to restore the or iginal gloss to a scratched, dull, or faded area. The finish of your boat should be thoroughly cleaned, buffed, and polished at least once each season. Take care when buffing or polishing with a marine cleaner not to over- heat the surface you are working, because you will burn it. 1-3 CONTROLLING CORROSION Since man first started out on the water, corrosion on his craft has been his enemy. The first form was merely rot in the wood and then it was rust, followed by other forms of destructive corrosion in the more modern materials. One defense against cor- rosion is to use similar metals throughout the boat. Even though this is difficult to do in designing a new boat, particularly the undersides, similar metals should be used whenever and wherever possible. A second defense against corrosion is to insulate dissimilar metals. This can be done by using an exterior coating of Sea Skin or by insulating them with plastic or rubber gaskets. · ········1.··. i l '" ,Ij Mercury outboard mounted on a boat in a dealer's showroom waiting to give a new owner hours of fun on the water.

1-2 SAFETY Zinc installation also used as the trim tab. The tab assists the helmsperson to maintain a true course without "fighting" the wheel. Using Zinc The proper amount of zinc attached to a boat is extremely important. The use of too much zinc can cause wood burning by plac- ing the metals close together and they be- come "hot". On the other hand, using too small a zinc plate will cause more rapid deterioration of the metal you are trying to protect. If in doubt, consider the fact that it is far better to replace the zincs than to replace planking or other expensive metal parts from having an excess of zinc. When installing zinc plates, there are two routes available. One is to install many Accessory zinc installation on the boat transom to provide additional corrosion protection. A new trim tab zinc, left, and a corroded zinc, right. An excellent example of the inexpensive zinc saving more costly parts of the outboard unit. different zincs on all metal parts and thus run the risk of wood burning. Another route, is to use one large zinc on the tran- som of the boat and then connect this zinc to every underwater metal part through internal bonding. Of the two choices, the one zinc on the transom is the better way to go. Small outboard engines have a zinc plate attached to the cavitation plate. Therefore, the zinc remains with the engine at all times. 1... PROPELLERS As you know, the propeller is actually what moves the boat through the water. This is how it is done. The propeller oper- ates in water in much the manner as a wood screw does in wood. The propeller "bites" into the water as it rotates. Water passes. between the blades and out to the rear in the shape of a cone. The propeller "biting" through the water in much the same manner as a wood auger is what propels the boat. Diameter and pitch are the two basic dimensions of a propeller. The diameter is measured across the circumference of a circle scribed by the propeller blades, as shown.

Diameter and Pitch Only two dimensions of the propeller are of real interest to the boat owner: the diameter and the pitch. These two dimen- sions are stamped on the propeller hub and always appear in the same order: the diam- eter first and then the pitch. For instance, the number 15-19 stamped on the hub, would mean the propeller had a diameter of 15 inches with a pitch of 19. The diameter is the measured distance from the tip of one blade to the tip of the other as shown in the accompanying illus- tration. The pitch of a propeller is the angle at which the blades are attached to the hub. This figure is expressed in inches of water travel for each revolution of the propeller. In our exam pIe of a 15-19 propeller, the propeller should travel 19 inches through the water each time it revolves. If the propel- ler action was perfect and there was no slippage, then the pitch multiplied by the propeller rpms would be the boat speed. Most outboard manufacturers equip their units with a standard propeller with a di- ameter and pitch they consider to be best sui ted to the engine and the boat. Such a propeller allows the engine to run as near to the rated rpm and horsepower (at full throt- tle) as possible for the boat design. The blade area of the propeller deter- mines its load-carrying capacity. A two- blade propeller is used for high-speed run- ning under very light loads. A four-blade propeller is installed in boats intended to operate at low speeds under very heavy loads such as tugs, barges, or large houseboats. The three-blade pro- peller is the happy medium covering the wide range between the high performance units and the load carrying workhorses. .-.--- 10" ----t~ mOPELLERS 1-3 Typical attaching hardware for a propeller. Propeller Selection There is no standard propeller that will do the proper job in very many cases. The list of sizes and weights of boats is almost endless. This fact coupled with the many boat-engine combinations makes the propel- ler selection for a specific purpose a diffi- cult job. In fact, in many cases the propel- ler is changed after a few test runs. Proper selection is aided through the use of charts set up for various engines and boats. These charts should be studied and understood when buying a propeller. However, bear in mind, the charts are based on average boats with average loads, therefore, it may be necessary to make a change in size or pitch, in order to obtain the desired results for the hull design or load condition. Propellers are available with a wide range of pitch. Remember, a low pitch takes a smaller bite of the water than the high pitch propeller. This means the low pitch propeller will travel less distance through the water per revolution. The low 21" --------~ Diagram to explain the pitch dimension of a propeller. The pitch is the theoretical distance a propeller would travel through water if there were no friction.

1-4 SAFETY pitch will require less horsepower and will allow the engine to run faster. All engine manufacturers design their units to operate with full throttle at, or slightly above, the rated rpm. If you run your engine at the rated rpm, you will increase spark plug life, receive better fuel economy, and obtain the best performance from your boat and engine. Therefore, take time to make the proper propeller selection for the rated rpm of your engine at full throttle with what you consider to be an average load. Your boat will then be cor- rectly balanced between engine and pro- peller throughout the entire speed rahge. A reliable tachometer must be used to measure engine speed at full throttle to ensure the engine will achieve full horse- power and operate efficiently and safely. Totes t for the correct propeller, make your run in a body of smooth water with the lower unit in forward gear at full throttle. If the reading is above the manufacturer's recommended operating range, you must try propellers of greater pitch, until you find the one that allows the engine to operate continually within the recommended full throttle range. If the engine is unable to deliver top performance and you feel it is properly tuned, then the propeller may not be to blame. Operating conditions have a marked effect on performance. For instance, an .') o 0 o Cavitation (air bubbles) formed at the propeller. Manufacturers are constantly fighting this problem, as explained in the text. engine will lose rpm when run in very cold water. It will also lose rpm when run in salt water as compared with fresh water. A hot, low-barometer day will also cause your en- gine to lose power. Cavitation Cavitation is the forming of voids in the water just ahead of the propeller blades. Marine propUlsion designers are constantly fighting the battle against the formation of these voids due to excessive blade tip speed and engine wear. The voids may be filled with air or water vapor, or they may actual- ly be a partial vacuum. Cavitation may be caused by installing a piece of equipment too close to the lower unit, such as the knot indica tor pickup, depth sounder, or bait tank pickup. Vibration Your propeller should be checked reg- ularly to be sure all blades are in good condition. If any of the blades become bent or nicked, this condition will set up vibra- tions in the drive unit and the motor. If the vibration becomes very serious it will cause a loss of power, efficiency, and boat perfor- mance. If the vibration is allowed to con- tinue over a period of time it can have a damaging effect on many of the operating parts. Vibra tion in boats can never be com- pletely eliminated, but it can be reduced by keeping all parts in good working condition and through proper maintenance and lubri- cation. Vibration can also be reduced in Example of a damaged propeller. This unit should have been replaced long before this amount of damage was sustained.