1993-1995 Mercury 90 HP and 120 HP Sport Jet Service & Repair Manual

Quick Reference Data GENERAL SPECIFICATIONS Engine type 90 hp 120 hp Bore Stroke 90 hp 120 hp Displacement 90 hp 120 hp Compression ratio Ignition system Cooling system Electricai system Jet pump Gear ratio 90 hp 120 hp impeller type impeller diameter 2-stroke, 3-cyilnder Inline 2-stroke, 4-cyilnder inline 3.375 in. (85.72 mm) 2.80 in. (71.12 mm) 2.876 in. (73.05 mm) 75.1 cid (1231 cc) 102.9 cid (1087 CO) 6.8:1 Capacitor discharge Thermostatic pressure controlled 12-Voit, negative ground Mixed flow, single stage 1.14:1 1.0:1 Stainless steei 5 blade 6.43 in. TUNE-UP Fuel-oH ratio (without oii injection) Recommended spark plug Spark plug gap Idle speed Recommended wide-open throttle range Initiai Idle mixture screw adjustment ignition timing Wide-open throttle At cranking speed Running at 5000 rpm Firing order 90 hp 120 hp Maximum spark advance at wide-open throttie Fuei pump pressure At idie At wide-open throttie Minimum battery rating SPECIFICATIONS 50:1 Champion L76V or Champion QL76V Surface gap 1100 rpm in neutral 4700-5300 rpm 1-1/2 turns out from lightiy seated 32° BTDC 30° BTDC 1-2-3 1-3-2-4 32° BTDC at cranking speed 30° BTDC at 5000 rpm 3.5 psi (24.1 kPa) 6psi(41.4kPa) 670 MCA or 520 CCA CAPACITIES Jet drive housing Stator OII reservoir (oii injection models) 18.6 fl.oz. (550 mL) 3.4fi.oz.(100mL) 4 qts. (3.81) VII

Introduction This Clymer shop manual covers the Mercury 90 and 120 hp Sport Jet propulsion system produced from 1993-1995. Troubleshooting, tune-up, maintenance and repair are not difficult, if you know what tools and equipment to use and how to perform the job. Step-by-step instructions guide you through jobs ranging from simple maintenance to complete engine, drive train and steering overhaul. This manual can be used by anyone from a first time do-it-yourselfer to a professional mechanic. Detailed drawings and clear photographs give you all the information you need to do the job right.

Chapter One General Information Special tools are required to perform some of the procedures in this manual. However, a re- sourceful mechanic may be able, in come cases, to fabricate an acceptable substitute for a particular special tool. This can be as simple as using a few pieces of threaded rod, washers and nuts to remove or install a bushing or bearing. However, using a substitute for a special tool is generally not recommended as it can cause personal injury and may damage the part. But, if you find that a tool can be designed, made and safely used, you may want to search out a local community col- lege or high school that has a machine shop curriculum. Shop teachers sometimes welcome outside work that can be used as practical shop applications for advance students. U.S. standard and metric measurements are used throughout this manual. Table 1 contains fractional, decimal and metric equivalents. Ta- ble 2 lists torque specifications for general fasteners. Tables 1-2 are found at the end of this chapter. MANUAL ORGANIZATION This chapter provides general information useful to Sport Jet owners and mechanics. In addition, information in this chapter discusses the tools and techniques used for preventive maintenance, troubleshooting and repair. Chapter Two provides troubleshooting methods and suggestions for quick and accurate diag- nosis and repair of problems. Troubleshooting procedures discuss typical symptoms and logical methods to pinpoint the trouble. Chapter Three explains the periodic lubrica- tion and routine maintenance necessary to keep your Sport Jet in top operating condition. Chap- ter Three also includes recommended tune-up

CHAPTER ONE procedures, eliminating the need to constantly consult other chapters on the various assemblies. Subsequent chapters describe specific systems, providing disassembly, repair, reassembly and adjustment procedures in simple step-by- step form. If a specific repair procedure is im- practical for a home mechanic, it is so indicated. In some cases, it could even be faster and less expensive to take such repairs to a dealer or qualified repair shop. Specifications concerning a specific system are located 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 addition information to make a step or procedure clearer or easier to understand. Disregarding a NOTE may cause inconvenience, but should not result in damage or personal injury. A CAUTION emphasizes areas where equipment damage might occur. 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 he taken seriously. Serious injury or death can result from disregarding warnings. SAFETY FIRST Professional mechanics can work for years and never sustain a serious injury. If you observe a few rules of common sense and safety, you too can enjoy many safe hours servicing your own machine. If you ignore these rules you can hurt yourself or damage the equipment. 1. Never use gasoline as a cleaning solvent. 2. Never smoke or use a torch in the vicinity of flammable liquids, such as cleaning solvent, and especially gasoline. 3. If welding or brazing is required on the machine, remove the fuel tank and move it to a safe distance, at least 50 ft. {15m) away. 4. Use the proper size wrenches to avoid damage to fasteners and injury to yourself. 5. When loosening a tight or stuck fastener, be guided by what would happen if the wrench should slip. Be careful and protect yourself ac- cordingly. 6. When replacing a fastener, make sure to use one with the same measurements and strength as the old one. Incorrect or mismatched fasteners can result in damage to the boat or propulsion unit and possible personal injury. Beware of fastener kits that are filled with cheap and poorly made nuts, bolts, washers and cotter pins. Refer to Fasteners in this chapter for additional information. 7. Keep all hand and power tools in good condition. Always clean greasy and oily tools after using them. Greasy or oily tools are difficult to hold and can cause injury. Replace or repair worn or damaged tools. 8. Keep your work area clean and uncluttered. 9. Wear safety goggles during all operations involving drilling, grinding, the use of a cold

GENERAL INEORMATION chisel, punch or anytime you feel unsure about the safety of your eyes. Safety goggles should also be worn anytime solvent and compressed air are used to clean parts. 10. Keep an approved fire extinguisher nearby. Be sure it is rated for gasoline (Class B) and electrical (Class C) fires. 11. When drying bearings or other rotating parts with compressed air, never allow the air jet to rotate the bearing or part. The air jet is capable of rotating them at speeds far in excess of those for which they were designed. The bearing or rotating part is very likely to disintegrate causing serious personal injury. To prevent bearing damage when using compressed air, hold the inner bearing race by hand. SERVICE HINTS Most of the service procedures covered are straightforward and can be performed by anyone reasonably skillful with tools. It is suggested, however, that you consider your own capabilities carefully before attempting any operation involving major disassembly. 1. "FRONT" as used in this manual, refers to the front or bow of the Sport Jet system or boat; the front of any component is the end closest to the front of the Sport Jet. The terms, "left-" and "right-hand" sides refer to the position of the propulsion system or parts as viewed when standing behind the boat engine and jet drive assembly. These rules are simple, but confusion can cause a major inconvenience during service. 2. When disassembling any engine or drive component, mark the parts for original location and direction. Mark all parts which mate to- gether, for location and direction. Small parts, such as bolts, can be identified by placing them in plastic sandwich bags. Seal the bags and label them with masking tape and a marking pen (Fig- ure 1). When reassembly will take place imme- diately, an accepted practice is to place nuts, screws, bolts and other fasteners in a cupcake tin or egg carton in the order of disassembly. 3. Finished surfaces should be protected from physical damage or corrosion. Keep gasoline and solvent off painted surfaces. 4. Use a suitable penetrating oil on frozen or tight bolts, then tap the bolt head a few times with a hammer and punch (use a screwdriver on screws). Avoid the use of heat where possible, as it can warp, melt or affect the temper (hardness) of the component. Heat also ruins finishes, especially paint and plastics. 5. No component removed or installed (other than bushings and bearings) in the procedures given in this manual should require unusual force during disassembly or reassembly. If a part is difficult to remove or install, find out why before proceeding. 6. Cover all openings after removing components or assemblies to prevent small tools, parts, dirt or other contamination from entering. 7. Read each procedure completely while look- ing at the actual parts before starting a job. Make sure you thoroughly understand what is required, then carefully follow the procedure, step-by- step. 8. Recommendations are occasionally made to refer service or maintenance to a Sport Jet dealer or a specialist in a particular field. In some cases, the work may even be done more quickly and economically than if you performed the job yourself. 9. In procedural steps, the term "replace" means to discard a defective part and replace it with a new or exchange unit. "Overhaul" means to remove, disassemble, inspect, measure, repair or replace defective parts, then reassemble and install major systems or parts. 10. Some operations require the use of a hydrau- lic or an arbor press. If a suitable press is not available, it would be wise to have these operations performed by a shop equipped for such work, rather than to try to do the job yourself

CHAPTER ONE with makeshift equipment that may damage your machine. 11. Repairs go much faster and easier if your machine is clean before you begin work. There are many special cleaners on the market for washing the engine and related parts. Follow the manufacturer's instructions on the container for the best results. Clean all oily or greasy parts with cleiining solvent as you remove them. WARNING Never use gasoline as a cleaning agent. It presents an extreme fire hazard. Be sure to work in a well-ventilated area when using cleaning solvent. Keep afire extinguisher, rated fi)r gasoline fires, handy in any case, 12. If special tools are necessary, make arrange- ments to obtain them before starting work. It is frustrating and time-consuming to get partially into a job, then be unable to complete it. 13. Make diagrams (or take a Polaroid picture) whenever similar parts are found. For example, crankcase bolts are often not the same length. You may think you can remember where every- thing came from, but mistakes can be costly. It is also possible that you may be sidetracked and not retum to the work for days or even weeks. During such time carefully arranged parts may become disturbed. 14. When reassembling parts, be sure all shims and washers are replaced exactly as they were removed. 15. Whenever a rotating part contacts a station- ary part, look for a shim or washer. 16. Always install new gaskets, seals and O- rings during reassembly. Gaskets are usually installed dry (without sealant), unless otherwise specified. 17. If it should become necessary to make a gasket, and the old gasket is not available for use as a guide, use the outline of the cover or part. Apply engine oil to the gasket surface, then place the part on the new gasket material. Apply pressure to the part and the oil will leave a very accurate outline on the gasket material. CAUTION If purchasing gasket material to fabricate a gasket, measure the thickness of the old gasket. The gasket material must have the same approximate thickness as the original gasket. 18. Heavy grease can be used to hold small parts in place if they tend to fall from position during assembly. Keep grease and oil away from electrical components, however. In addition, any

GENERAL INFORMATION grease used inside the power head must be gasoline soluble. 19. A carburetor is best cleaned by disassembling it and soaking the parts in a commercial carburetor cleaner. Never soak gaskets and rub- ber parts in these cleaners. Never use v^ire to clean carburetor jets and air passages. Use compressed air to blow out the carburetor passages. 20. Most of all, take your time and do the job right. Do not forget that a newly rebuilt engine must be correctly broken-in, just like a new one. ENGINE OPERATION All Mercury Sport Jet models are equipped with a 2-stroke marine engine. During this dis- cussion, assume that the crankshaft is rotating counterclockwise in Figure 2. As the piston travels downward, a transfer port (A, Figure 2) between the crankcase and cylinder is uncov- ered. The exhaust gases leave the cylinder through the exhaust port (B, Figure 2), which is also opened by the downward movement of the piston. A lightly compressed, fresh fuel-air charge travels from the crankcase (C, Figure 2) to the cylinder through the transfer port (A) as the port opens. Since the incoming charge is under pressure, it rushes into the cylinder quickly and helps to scavenge (expel) the exhaust gases from the previous combustion. Figure 3 illustrates the next phase of the cycle. As the crankshaft continues to rotate, the piston moves upward, closing the exhaust and transfer ports. As the piston continues upward, the air- fuel mixture in the cylinder is compressed. No- tice also that a vacuum is being created in the crankcase at the same time. Further upward piston movement uncovers the intake port (D, Fig- ure 3). A fresh fuel-air charge is then drawn into the crankcase through the intake port because of the vacuum created by the upward piston movement. The third phase is shown in Figure 4. As the piston approaches top dead center (TDC), the spark plug fires, igniting the compressed fuel-air mixture. The piston is then driven downward by the expanding gases. When the top of the piston uncovers the exhaust port, the fourth phase begins. The exhaust gases leave the cylinder through the exhaust port. As the piston continues downward, the intake port is closed and the mixture in the crankcase is compressed in preparation for the next cycle.

CHAPTER ONE TORQUE SPECIEICATIONS Torque specifications throughout this manual are given in foot-pounds (ft.-lb.) and Newton- meters (N.m). Table 2 lists general torque specifications for nuts and bolts that are not listed in the respective chapters. To use the table, first determine the size of the fastener by measuring it with a vernier caliper. See Eigure 5 and Eigure 6. EASTENERS The design and material used to manufacture the various fasteners used on your Sport Jet system is not selected by chance or accident. Fastener design determines the type of tool required to tum the fastener. Fastener material is carefully selected to decrease the possibility of physical failure from breakage, corrosion or other factors. 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 on both are properly matched. The best way to determine if the threads on 2 fasteners are matched is to tum the nut on the bolt (or the bolt into a threaded hole) using the fingers only. Be sure the threads on both fasteners are clean and undamaged. 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. A thread pitch gauge can also be used to determine thread pitch. See Eigure 7. Mercury Sport Jets are manufactured with U.S. standard and metric fasteners. Most threads are cut so the fastener must be turned clockwise to tighten it. These are called right-hand threads. Some fasteners have left- hand threads; they must be turned counterclockwise to tighten. Left-hand threads are used in locations where normal rotation of the equipment would tend to loosen a right-hand threaded fastener. ISO Metric Screw Threads ISO (International Organization for Stand- ardization) metric threads are available in 3 standard thread sizes: coarse, fine and constant pitch. The ISO coarse pitch is used for most common fastener applications. The fine pitch thread is used on certain precision tools and

GENERAL INFORMATION instruments. The constant pitch thread is used mainly on machine parts and is not generally used on fasteners. The constant pitch thread is, however, used on all metric thread spark plugs. ISO metric threads are specified by the capital letter M followed by the diameter in millimeters and the pitch (or distance between each thread) in millimeters separated by the sign "x." For example a M8 x 1.25 bolt is one that has a diameter of 8 millimeters with a distance of 1.25 millimeters between each thread. The measurement across 2 flats on the head of the bolt indicates the proper wrench size used to turn the fastener. Figure 11 shows how to determine bolt diameter. NOTE When purchasing a bolt from a dealer or parts store, it is important to know how to specify bolt length. The correct way to measure bolt length is by measuring the length starting from under the bolt head to the end of the bolt. Always measure bolt length in this manner to avoid purchasing bolts that are too long or too short. Machine Screws There are many different types of machine screws. Figure 8 shows a number of screw heads which require different types of tools to turn them. The screw heads are also designed to either protrude above the metal (round) or to be slightly recessed (flat) in the metal. See Figure 9. Bolts Commonly called a bolt, the correct technical name for this type of fastener is cap screw. U.S. standard bolts are described by the diameter, length and threads per inch. OPENINGS FOR TURNING TOOLS Slotted Phillips Allen Internal Tone Extrnal Torx MACHINE SCREWS

CHAPTER ONE Nuts Nuts are manufactured in a variety of types and sizes. Most are hexagonal (6 sides) and fit on bolts, screws and studs having the same diameter and pitch. Figure 10 shows several types of nuts. The common nut is generally used with a lockwasher. Self-locking nuts have a nylon insert which pre- vents the nut from loosening. Self-locking fasteners do not normally require lockwashers. Wing nuts are designed for fast removal by hand and are used for convenience in noncritical locations. To indicate the size of a nut, manufacturers specify the diameter of the opening and threads per inch (coarse or fine threads). This is similar to bolt specifications, but without the length dimension. The measurement across 2 flats on the nut indicates the proper wrench size used to tum the nut. Self-Locking Fasteners Several types of bolts, screws and nuts incor- porate a system that develops an interference between the bolt, screw, nut or threaded hole. Interference is achieved in various ways: by slightly distorting the threads, coating the threads with dry adhesive or nylon, or distorting the top of an all-metal nut. Self-locking fasteners offer greater holding strength and better vibration resistance than a plain nut and lockwasher. Some self-locking fasteners can be reused if still in good condition. Others, like the nylon insert nut, form an initial locking condition when the nut is first installed. Once installed, however, the nylon insert con- forms closely to the bolt thread pattern. There- fore, once the fastener is removed, it should be replaced to offer the greatest security. Washers There are 2 basic types of washers: flat washers and lockwashers. Flat washers are simple discs with a hole to fit a screw, bolt or stud. Lockwashers are designed to prevent a fastener from working loose due to causes such as vibration, expansion or contraction. Figure 11 shows several types of washers. Washers are also used in the following functions: a. As spacers. Common nut Self-locking nut Wing nut Plain Folding Internal tooth External tooth

1993-1995 Mercury 90 HP and 120 HP Sport Jet Service & Repair Manual

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