Book Excerpt: 2005-2010 Yamaha 4-Stroke Outboard Repair Manual FUEL SYSTEMS
FUEL INJECTION BASICS
(See Figures 74 and 74) Fuel injection is not a new invention. Even as early as the 1950s, various automobile manufacturers experimented with mechanical-type injection systems. There was even a vacuum tube-equipped control unit offered for one system! This might have been the first "electronic fuel injection system." Early problems with fuel injection revolved around the control components. The electronics were not very smart or reliable. These systems have steadily improved since. Today's fuel injection technology, responding to the need for better economy and emission control, has become amazingly reliable and efficient. Computerized engine management, the brain of fuel injection, continues to get more reliable and more precise. Components needed for a basic computer-controlled system are as follows:
- A computer-controlled engine manager, which is the Electronic Control Module (ECM), with a set of internal maps to follow (you know, if this, then do that type of information for the fuel and ignition systems).
- A set of input devices to inform the ECM of engine performance parameters.
- A set of output devices. Each device is controlled by the ECM. These devices modify fuel delivery and timing. Changes to fuel injection and timing are based on input information matched to the map programs.
2.5 AND 4 HP POWERHEADS POWERHEAD REMOVAL AND INSTALLATION
(See figures 5, 6 and 7) These powerheads are small enough that you can remove them from the intermediate housing without removing most fuel and electrical components. However, Yamaha specifically directs their technicians to remove those components, though it seems more likely that they do this because removal will be necessary for whatever type of service is conducted on the powerhead after removal. We advise that you consider why the powerhead is being removed. If you are planning on disassembling the powerhead for inspection or overhaul, then you'll have to remove the fuel and electrical components anyway. If this is the case, removing them before powerhead removal is a good idea, if only to protect them from potential damage when lifting and moving the powerhead itself. However, the choice remains yours whether or not you follow all of the initial steps for stripping the powerhead of these components.
- Remove the engine top cowling.
- If desired, remove the hand-rewind starter assembly and flywheel from the powerhead.
- On 2.5 hp models, remove the lower cowling as follows:
- Loosen the throttle cable stop screw on the carburetor throttle valve, and then remove the throttle cable from the carburetor.
- Loosen the 2 bolts and remove the outboard carrying handle.
- Unbolt and remove the fuel cock from the carburetor fuel cock lever. Keep track of the lever O-ring and replace if warn or damaged.
- Locate and remove the fasteners securing the front and rear halves of the bottom cowling. There are usually 4 bolts threaded upward from underneath the cowling (each through a collar and grommet) and 2 bolts at the top flange threaded sideways from one cowling half to the other into spring nuts on tabs.
Subject: 2005, 2006, 2007, 2008, 2009, 2010 Yamaha 2.5-350 HP V6, V8 4-stroke outboard motor service, maintenance, repair. ISBN-10: 0893300802 | ISBN-13: 9780893300807 | Seloc 1707
- General information
- Tools and equipment
- Boating safety
- Engine tune-up
- Engine disassembly and reassembly
- Fuel system
- Ignition system
- Electrical system
- Cooling system
- Drive unit
- Tilt and trim systems
- Engine specs; torque specs
- Maintenance and off-season storage
- Wiring diagrams