1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Yamaha Outboard Carburetor Repair, Adjustment, Rebuilding and Tuning Service Manual.

 


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Timing and synchronization on an outboard engine is extremely important to obtain maximum efficiency. The powerhead cannot perform properly and produce its designed horsepower output if the fuel and ignition systems have not been redissolve dusted. towards equipped with a negativeness type ignition  (CDI) system use a series of link rods between the carburetor and the ignition base date assembly. At the time the throttle is opened. the ignition base plate assembly is coated by means of the link rod, thus advancing timing.

On electronically controlled ignition models, a microcomputer decides when to advance or retard the timing based on input from various sensors. Therefore, there is no link rod between the magneto control lever and the stator assembly. Many models have timing marks on the flywheel and CDI base. A timing light is normally used to check the ignition timing with the powerhead operating (dynamically). An alternate method is to check the timing with the powerhead not operating (static timing). This second method requires the use of a dial indicator gauge.

Various models have unique methods of checking ignition timing. As appropriate, these differences will be explained in detail in the text. In simple terms, synchronization is timing the fuel system to the ignition. As the throttle is advanced to increase powerhead rpm, the fuel and the ignition systems are both advanced equally and at the same rate. Any time the fuel system or the ignition system on a power head is serviced to replace a faulty part o; any adjustments are made for any reason, powerhead timing and synchronization must be carefully checked and verified.

On the breaker point ignitions, synchronization is automatic once the point gap and the piston travel or timing mark alignments are correct. Models equipped with electronic ignitions are statically timed by aligning the timing marks on the throttle cam or throttle stopper with timing marks on the flywheel. Initial timing and timing advance are both set this way before using a timing light to check the timing. The throttle cam adjustment cannot be made unless the carburetor throttle shutter is completely closed. Therefore, the idle speed screw may have to be backed out; the despot adjusted away from the throttle cam; and or the neutral RPM screw rotated counterclockwise before a proper throttle cam roller alignment can be made.

2. With the engine shut down, move the throttle cam to check the cam adjustment. The bottom scribe line on the cam should be aligned with the center of the throttle roller and the roller just barely touches the cam.

3. If an adjustment is necessary, first loosen the hex bolt and with the punch mark on the eccentric facing down and forward of the hex bolt axis, rotate the eccentric counter clockwise to reposition the cam until the throttle roller is aligned with the scribe line.

Traditional carburetor theory often involves a number of laws and principles. The diagram illustrates several carburetor basics. If you blow air across a straw inserted into a container of liquid, a pressure drop is created in the straw column. As the liquid in the column is expelled, an atomized mixture (air and fuel droplets) is created. In a carburetor this is mostly air and a little fuel. The actual ratio of air to fuel differs with engine conditions but is usually from 15 parts air to one part fuel at optimum cruise to as little as 7 parts air to one part fuel at full choke.

Using our example, what if the top of the container is covered and sealed around the straw, what will happen? No flow. This is typical of a clogged carburetor bowl vent. If the base of the straw is clogged or restricted what will happen? No flow or low flow. This represents a clogged main jet. If the liquid in the glass is lowered and you blow through the straw with the same force what will happen? Not as much fuel will flow. A lean condition occurs. If the fuel level is raised and you blow again at the same velocity what happens? The result is a richer mixture.

The carburetor is merely a metering device for mixing fuel and air in the proper proportions for efficient engine operation. At idle speed, an outboard engine requires a mixture of about 8 parts air to 1 part fuel. At high speed or under heavy duty service, the mixture may change to as much as 12 parts air to 1 part fuel. Float Systems A small chamber in the carburetor serves as a fuel reservoir. A float valve admits fuel into the reservoir to replace the fuel consumed by the engine. If the carburetor has more than one reservoir, the fuel level in each reservoir (chamber) is controlled by identical float systems.

Fuel level in each chamber is extremely critical and must be maintained accurately. Accuracy is obtained through proper adjustment of the floats. This adjustment will provide a  balanced metering of fuel to each cylinder at all speeds. Following the fuel through its course, from the fuel tank to the combustion chamberof the cylinder, will provide an appreciation of exactly what is taking place. In order to start the engine, the fuel must be moved from the tank to the carburetor by a squeeze bulb installed $I the fuel line. This action is necessary because the fuel pump does not have sufficient pressure to draw fuel from the tank during cranking before the engine starts. The fuel for some small horsepower units is gravity fed from a tank mounted at the rear of the powerhead. Even with the gravity feed method, a small fuel pump may be an integral part of the carburetor.
After the engine starts, the fuel passes through the pump to the carburetor.


All systems have some type of filter installed somewhere in the line between the tank and the carburetor. Many units have a filter as an integral part of the carburetor. At the carburetor, the fuel passes through the inlet passage to the needle and seat and then into the float chamber (reservoir). A float in the chamber rides up and down on the surface of the fuel. After fuel enters the chamber and the level rises to a predetermined point, a tang on the float closes the inlet needle and the flow entering the chamber is cut off. When fuel leaves the chamber as the engine operates, the fuel level drops and the float tang allows the inlet needle to move off its seat and fuel once again enters the chamber. In this manner, a constant reservoir of fuel is maintainedn in the chamber to satisfy the demands of the engine at all speeds.


A fuel chamber vent hole is located near the top of the carburetor body to permit atmospheric pressure to act against the fuel in each chamber. This pressure assures an adequate fuel supply to the various operating systems of the powerhead. A suction effect is created each time the piston moves upward in the cylinder. This suction draws air through the throat of the carburetor. A restriction in the throat, called a venture, controls air velocity and has the effect of reducing air pressure at this point. The difference in air pressures at the throat and in the fuel chamber, causes the fuel to be pushed out of metering jets extending down into the fuel chamber. When the fuel leaves the jets, it mixes with the air passing through the venture. This fuel air mixture should then be in the proper proportion for burning in the cylinders for maximum engine performance.


In order to obtain the proper air fuel mixture for all engine speeds, some models have high and low speed jets. These jets have adjustable needle valves which are used to compensate for changing atmospheric conditions. In almost all cases, the high-speed circuit has fixed high-speed jets and are not adjustable. A throttle valve controls the flow of air fuel mixture drawn into the combustion chambers. A cold powerhead requires a richer fuel mixture to start and during the brief period it is warming to normal operating temperature. A choke valve is placed ahead of the metering jets and venture. As this valve begins to close, the volume of air intake is reduced, thus enriching the mixture entering the cylinders.
When this choke valve is fully closed, a very rich fuel mixture is drawn into the cylinders.

The throat of the carburetor is usually referred to as the barrel. Carburetors with single, double or four barrels have individual metering jets, needle valves, throttle and choke plates for each barrel. Single and two barrel carburetors are fed by a single float and chamber.


1984-1994 Yamaha Outboard Service Manual/WorkShop Manual Application: 2 hp 1 cyl. (43cc) 2-stroke 1984 1994, 3 hp 1 cyl. (70cc) 2-stroke 1989, 3 hp 1 cyl. (70cc) 2-stroke 1990 1994, 4 hp 1 cyl. (83cc) 2-stroke 1984 1994, 5 hp 1 cyl. (103cc) 2-stroke 1984 1994, 6 hp 2 cyl. (165cc) 2-stroke 1986 1994, 8 hp 2 cyl. (165cc) 2-stroke 1984 1994, 9.9 hp 2 cyl. (246cc) 2-stroke 1984 1994, 9.9 hp 2 cyl. (232cc) 4-stroke 1984 1994, 15 hp 2 cyl. (246cc) 2-stroke 1984 1994, 25 hp 2 cyl. (395cc) 2-stroke 1988 1994, 25 hp 2 cyl. (430cc) 2-stroke 1990 1994, 25 hp 2 cyl. (496cc) 2-stroke 1984 1994, 28 Jet 3 cyl. (698cc) 2-stroke 1990 1994, 30 hp 2 cyl. (496cc) 2-stroke 1984 1994, 30 hp 3 cyl. (496cc) 2-stroke 1987 1994, 35 Jet 3 cyl. (698cc) 2-stroke 1987 1994, 40 hp 2 cyl. (592cc) 2-stroke 1989 1994, 40 hp 3 cyl. (698cc) 2-stroke 1984 1994, 50 hp 3 cyl. (698cc) 2-stroke 1984 1994, 50 hp 3 cyl. (849cc) 2-stroke 1994 1994, 55 hp 2 cyl. (760cc) 2-stroke 1989 1994, 60 hp 3 cyl. (849cc) 2-stroke 1991 1992 1993 1994, 65 Jet 3 cyl. (1140cc) 2-stroke 1987 1994, 70 hp 3 cyl. (849cc) 2-stroke 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994, 75 hp 3 cyl. (1140cc) 2-stroke 1994, 80 hp 3 cyl. (1140cc) 2-stroke 1994, 80 Jet V4 (1730cc) 2-stroke 1987 1994, 85 hp 3 cyl. (1140cc) 2-stroke 1989 1994, 90 hp 3 cyl. (1140cc) 2-stroke 1984 1994, 115 hp V4 (1730cc) 2-stroke 1984 1994, 130 hp V4 (1730cc) 2-stroke 1988 1994, 140 hp V4 (1730cc) 2-stroke 1984 1994, 140 Jet V6 (2596cc) 2-stroke 1987 1994, 150 hp V6 (2596cc) 2-stroke 1984 1994, 175 hp V6 (2596cc) 2-stroke 1984 1994, 200 hp V6 (2596cc) 2-stroke 1984 1994, 220 hp V6 (2596cc) 2-stroke 1984 1985 1986 1987, 225 hp 76 deg. V6 (3130cc) 2-stroke 1994, 225 hp 90 deg. V6 (2596cc) 2-stroke 1987 1988 1989 1990 1991 1992 1993 1994, 250 hp V6 (3130cc) 2-stroke 1990 1994

LIT-18616-01-24 Service Manual Application: Yamaha Ouboard 9.9HP (9.9-HP) 4-stroke engines. Model Names: T9.9T (T9.9-T), F9.9T (F9.9T), T9.9MH (T9.9-MH), F9.9AM (F9.9-AM), F9.9AEM (FT9.9-AEM), T9.9ER (T9.9-ER), F9.9AE (F9.9-AE), F9.9MH (F9.9-MH), F9.9BM (F9.9-BM), T9.9EH (T9.9-EH), F9.9BEM (F9.9-BEM), F9.9BE (F9.9-BE).

LIT-18616-01-28 Service Repair Manual Application: 1995, 1996, 1997 (95, 96, 97) Yamaha Marine Outboard E48T (E48-T) C55T (C55-T) 48HP & 55HP 2-Stroke. Item Model Names: E48T, C55T, E48C, E48MH, E55C, 55BM, C55ER, 55BE, 55BEM, C55TR, 55BET.

LIT-18616-01-35 Service Manual Application: 1996-1997 Yamaha F8, T9.9, F9.9 8HP (8-hp) & 9.9Hp (9.9-hp) 4-stroke engines. Exact Models Covered (Covers All 1996-1997 Models World Wide): F8B (F8-B), F9.9A (F9.9-A), F9.9B (F9.9-B), T9.9U (T9.9-U), F9.9U (F9.9-U), F8BM (F8-BM), F8BEM (F8-BEM), F8BE (F8-BE), T9.9MH (T9.9-MH), T9.9AM (T9.9-AM), FT9.9AMH (FT-9.9-AMH), T9.9EH (T9.9-EH), F9.9AEM (FT9.9-AEM), T9.9ER (T9.9-ER), FT9.9AE (FT9.9-AE), F9.9MH (F9.9-MH), F9.9BM (F9.9-BM), F9.9EH (F9.9-EH), F9.9BEM (F9.9-BEM), F9.9BE (F9.9-BE).

LIT-18616-01-29 Service Repair Manual Application: 1996, 1997 (96, 97) E60, E60H 60HP (60-HP) Yamaha Marine Outboard 2-Stroke. Item Model Names: E60, E60H, E60HM, E60HE, E60HEM, E60MH, E60EH. Covers USA, Canada and wold wide models.

LIT-18616-01-73 Service Repair Manual Application: 1997 97' Yamaha Marine Outboard 75HP (75HP) 2-Stroke. Item Model Names: E75V, E-75-V, E75-V, E-75V 75AM, 75AEM, 75AE, 75AET, 85AEM, 85AE, 85AET, E75B, E60J, E75MH. Covers USA, Canada and wold wide models.

LIT-18616-01-66 Service Repair Manual Application: 1997-1998 Yamaha Marine Outboard 20HP (20-HP) & 25HP 25-HP) 10V, 25V, 25V2 2-Stroke Engines. Model Names 20DM (20-DM), 20DMO (20-DMO), 20DEM (20-DEM), 20DEMO (20-DEMO), 20DERO (20-DERO), 20MH (20-MH), 20MH2 (20-MH2), 20EH (20-EH), 20EH2 (20-EH2), 25DM (25-DM), 25NMO (25-NMO), 25NEMO (25-NEMO), 25NE (25-NE), 25NEO (25-NEO), 25NERO (25-NERO), 25MH (25-MH), 25MH2 (25-MH2), 25EH (25-EH), 25ER (25-ER).

LIT-18616-01-81 Service Repair Manual Application: 1998-1999 98-99 40HP (40-HP) & 50HP (50-HP) 40W 50W Yamaha Marine Outboard 2-Stroke Item Model Names: 40-W, 50-W, 40VMH, 40VMHD, 40VMHO, 40VMO, 40VWH, 40VE, 40VEO, 40VEHTO, 40VET, C40MH, 40MH, C40ER, 40ER, P40TH, C40TR, 40VETO, 50HMHO, 50HMHD, 50HMO, 50HMDO, 50HWHD, 50HEDO, 50HET, 50HETO, 40TR, 50ER, C50TR, 50TR Covers USA, Canada and wold wide models.

LIT-18616-F1-50 & LIT-18616-02-12 Service Repair Manual Application: 1998-2005 Yamaha Marine Outboard 15HP (15-HP) 4-Stroke Engines F15W (F15-W), F15Z (F15-Z) 1998, 1999, 2000, 2001, 2002, 2003, 2004 & 2005. This manual covers all 15HP 4-Stroke models world wide including USA CANADA. USA & CANADA MODELS: F15MHW (F15-MHW), F15EHW (F15-EHW), F15AMH (F15-AMH), F15AEH (F15-AEH), F15AEP (F15-AEP), F15AEHP (F15-AEHP), F15PR (F15-PR), F15PH (F15-PH), F15AEP (F15-AEP), F15AEHP (F15-AEHP). WOLD WIDE MODELS: F15AMH (F15-AMH), F15AEH (F15-AEH), F15AE (F15-AE).

LIT-18616-01-83 Service Manual Application: 1998-2006 Yamaha F8, T9.9, F9.9 8HP (8-hp) & 9.9Hp (9.9-hp) 4-stroke engines for 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 & 2006. Model Name: T9.9W (T9.9-W), F9.9W (F9.9-W), F8BMH (F8-BMH), F8BEH (F8-BEH), F8BE (F8-BE), T9.9MH (T9.9-MH) FT9.9AMH (FT-9.9-AMH), T9.9EH (T9.9-EH), FT9.9AEH (FT9.9-AEH), T9.9ER (T9.9-ER), FT9.9AE (FT9.9-AE), F9.9MH (F9.9-MH), F9.9BMH (F9.9-BMH), F9.9EH (F9.9-EH), F9.9BEH (F9.9-BEH), F9.9BE (F9.9-BE).

LIT-18616-01-79 Service Repair Manual Application: 1998-2005 Yamaha Marine Outboard 4HP (4-HP) 4-Stroke Engines F4X (F4-X, F-4X) 1999, 2000, 2001, 2002, 2003, 2004 & 2005. This manual covers all 4HP 4-Stroke models world wide including F4MSHX, F4MLHX, F4AMH, USA CANADA.

LIT-18616-01-94 Service Repair Manual Application: 1999-2000 99-00 25HP (25-HP) & 30HP (30-HP) 25X, 25-X, 30X, 30-X, 25J, 25-J, 30D, 30-D Yamaha Marine Outboard 2-Stroke. Model Names: 25JMH, 25MH3, 30DMH, 25JMHO, 30DMHO, 30MH, 25JEHO, 25EH3, 30DWH, 25JEO, 25JETO, 25TR3, 30DEHO, 30EH, 30DMO, 30DE, 30DEO, 30ER, 30DET, 30DETO, 30TR Covers USA, Canada and wold wide models.

LIT-18616-01-96 Service Repair Manual Application: 1999, 2000, 2001, 2002 99, 00, 01, 02 100HP (100-HP) F100X, F100-X, F-100X Yamaha Marine Outboard 4-Stroke. Model Names: F100TR, F100-TR, F-100TR, F100AET, F-100AET, F100-AET Covers USA, Canada and woldwide models.

LIT-18616-02-16 Service Repair Manual Application: 2000, 2001, 2002, 2003, 2004, 2005, 2006, 00, 01, 02, 03, 04, 05, 06 Yamaha Marine Outboard 40HP (40-HP) F40B (F-40B-F40-B) 4-Stroke Engines. Model name F40BMHD, F40BWHD, F40BED, F40BET, USA and Canada name F40MH, F40ER, F40TR.

LIT-18616-02-19 Service Repair Manual Application: 2001, 2002, 2003, 2004, 2005, 2006, 01, 02, 03, 04, 05, 06, Yamaha Marine Outboard 6HP & 8HP (F6Z F8Z) 4-Stroke Engines. Model Name: F6AMH, F8CMH, F6MH, F8MH (F6-AMH, F6-MH, F8-AMH, F8-MH).

ALL 250HP 2003-2006 MODELS Service Repair Manual Application: 2003, 2004, 2005, 2006 Yamaha Marine Outboard 250HP (250-HP) 2-Stroke & 4-Stroke Engines. LIT-18616-02-78 - 2004-2005 Z250C & LZ250C LZ250TR 2-STROKE ENGINE. LIT-18616-02-43 - 2003-2005 Z250B & LZ250B MODEL NAME Z250TR/LZ250TR 2-STROKE ENGINE. LIT-18616-02-97 - 2005-2006 F250 & LF250 F250TR/LF250TR 4-STROKE ENGINE.

LIT-18616-02-54 Service Repair Manual Application: 2004, 2005, 2006 Yamaha Marine Outboard 2.5HP (2.5-HP) F2.5C (F2.5-C, F 2.5C) F2.5MH 4-Stroke Engines.

LIT-1816-02-59 Service Repair Manual Application: 2004, 2005, 2006 Yamaha Marine Outboard 9.9HP & 15HP (9.9-HP 15-HP) 2-Stroke Engines. Model name 9.9CMH & 15CMH ( 9.9 & 15 CMH).

LIT-18616-02-61 Service Repair Manual Application: 2004-2006 Yamaha Marine Outboard 25HP (25-HP) 4-Stroke Engines F25C, T25C (F-25C F25-C T25-C T-25C) F25MH, F25EH, F25ER, F25TR, T25TR.

LIT-18616-02-65 Service Repair Manual Application: 2004-2006 Yamaha Marine Outboard 40HP (40-HP) & 50HP (50-HP) 4-Stroke Engines. Exact model name 40VETO 50HETO, Both USA and CANADA models covered 40TR 50TR / 40C-50C.

LIT-18616-02-66 Service Repair Manual Application: 2004 2005 2006 Yamaha Marine Outboard 70HP (70-HP) 2-Stroke Engines. Model name 70BETO, USA and Canada name 70TR 70C (70-C).

LIT-18616-02-66 Service Repair Manual Application: 2004 2005 2006 Yamaha Marine Outboard 90HP (90-HP) 2-Stroke Engines. Model name 90AETO, USA and Canada name 90TR 90C (90-C).

LIT-18616-02-72 Service Repair Manual Application: 2004-2005-2006 Yamaha Marine Outboard 130HP & 115HP (115C 130C) 2-Stroke Engines. Model Name: 115CETO (115-CETO), 130BETO (130-BETO) 115TR, 130TR.

LIT-18616-02-51 Service Repair Manual Application: 2004, 2005, 2006 Yamaha Marine Outboard 150HP (150-HP) F150C & LF150C (LF-F-150C-F150-C) 4-Stroke Engines. Model name F150TR, LF150TR (F-LF-150-TR)

LIT-18616-02-71 Service Repair Manual Application: 2004, 2005, 2006 Yamaha Marine Outboard 115HP (115-HP) 4-Stroke Engines. Model name F115AET LF115AET, USA and Canada name F115TR LF115TR.

LIT-18616-02-73 Service Repair Manual Application: 2004-2005-2006 Yamaha Marine Outboard 150 HP (150HP) 150C & V150C 2-Stroke Engines. Model Name: 150FETO, 150GETO.

LIT-18616-02-66 Service Repair Manual Application: 2004 2005 2006 Yamaha Marine Outboard 60HP (60-HP) 2-Stroke Engines. Model name 60FETO USA and Canada name 60TR, 60C (60-C).

LIT-18616-02-76 Service Repair Manual Application: 2004-2006 Yamaha Marine Outboard F200C, LF200C, F225C, LF225C 200HP (200-HP) & 225HP (225-HP) V6 4-Stroke Engines.

LIT-18616-02-85 Service Repair Manual Application: 2005-2006 Yamaha Marine Outboard 50HP & 60HP (50-HP, 60-HP) 4-Stroke Engines F50D T50D F60D T60D (F-50-D, T-50-D, F60-D, T60-D).

LIT-18616-02-86 Service Repair Manual Application: 2005-2006 05-06' Yamaha Marine Outboard F90D 90HP 4-Stroke Engines. Model Name F90TR