Yamaha F4B User manual

SERVICE MANUAL
6BV-28197-3M-11
F4B
F5A
F6C

Preface
This manual has been prepared by Yamaha primarily for use by Yamaha dealers and their trained
mechanics when performing maintenance procedures and repairs to Yamaha equipment. It has
been written to suit the needs of persons who have the Bronze Technical Certificate of the YTA
(Yamaha Technical Academy) marine or the equivalent basic understanding of the mechanical and
electrical concepts and procedures inherent in the work, for without such knowledge attempted
repairs or service to the equipment could render it unsafe or unfit for use.
Because Yamaha has a policy of continuously improving its products, models may differ in detail
from the descriptions and illustrations given in this publication. Use only the latest edition of this
manual. Authorized Yamaha dealers are notified periodically of modifications and significant
changes in specifications and procedures, and these are incorporated in successive editions of this
manual. Also, up-to-date parts information is available on YPEC-web. Additional information and up-
to-date information on Yamaha products and services are available on Yamaha Service Portal.
Important information
Particularly important information is distinguished in this manual by the following notations:
The Safety Alert Symbol means ATTENTION! BECOME ALERT! YOUR SAFETY IS
INVOLVED!
A WARNING indicates a hazardous situation which, if not avoided, could result in death or
serious injury.
A NOTICE indicates special precautions that must be taken to avoid damages to the out-
board motor or other property.
TIP:
A TIP provides key information to make procedures easier or clearer.
F4B, F5A, F6C
SERVICE MANUAL
©2019 by Yamaha Motor Co., Ltd.
3rd Edition, January 2019
All rights reserved.
Any reprinting or unauthorized use
without the written permission of
Yamaha Motor Co., Ltd.
is expressly prohibited.

Contents
General information GEN
INFO 0
Specification SPEC 1
Technical features and description TECH
FEA 2
Rigging information RIG
GING 3
Troubleshooting TRBL
SHTG 4
Electrical system ELEC 5
Fuel system FUEL 6
Power unit POWR 7
Lower unit LOWR 8
Bracket unit BRKT 9
Maintenance MNT 10
Index
Appendix A

GEN
INFO
0
1
2
3
4
5
6
7
8
9
10
A
General information 0
Safety while working .................................................... 0-1
Rotating part .............................................................................. 0-1
Hot part ...................................................................................... 0-1
Electric shock ............................................................................ 0-1
Propeller .................................................................................... 0-1
Handling of gasoline .................................................................. 0-1
Ventilation .................................................................................. 0-1
Self-protection ........................................................................... 0-2
Working with crane .................................................................... 0-2
Part, lubricant, and sealant ........................................................ 0-2
Handling of sealant .................................................................... 0-2
Special service tool ................................................................... 0-2
Tightening torque ...................................................................... 0-3
Non-reusable part ...................................................................... 0-3
Disassembly and assembly ....................................................... 0-3
How to use this manual .................................................... 0-4
Manual format ........................................................................... 0-4
Abbreviation .............................................................................. 0-5
Lubricant, sealant, and thread locking agent ................. 0-6
Symbol ...................................................................................... 0-6
Special service tool ........................................................... 0-7

0-1
GEN
INFO
General information
Safety while working
To prevent an accident or injury and to pro-
vide quality service, observe the following
safety procedures.
Rotating part
• Hands, feet, hair, jewelry, clothing, personal
flotation device straps, and so on, can
become entangled with internal rotating
parts of the engine, resulting in serious
injury or death.
• Keep the top cowling installed whenever
possible. Do not remove or install the top
cowling when the engine is running.
• Only operate the engine with the top cowl-
ing removed according to the specific
instructions in the manual. Keep hands,
feet, hair, jewelry, clothing, personal flota-
tion device straps, and so on, away from
any exposed moving parts.
Hot part
During and after operation, engine parts are
hot enough to cause burns. Do not touch any
parts under the top cowling until the engine
has cooled.
Electric shock
Do not touch any electrical parts while start-
ing or operating the engine. Otherwise, shock
or electrocution could result.
Propeller
Do not hold the propeller with your hands
when loosening or tightening the propeller
nut.
Handling of gasoline
• Gasoline is highly flammable. Keep gaso-
line and all flammable products away from
heat, sparks, and open flames.
• Gasoline is poisonous and can cause injury
or death. Handle gasoline with care. Never
siphon gasoline by mouth. If you swallow
some gasoline, inhale a lot of gasoline
vapor, or get some gasoline in your eyes,
see your doctor immediately. If gasoline
spills on your skin, wash with soap and
water. If gasoline spills on your clothing,
change your clothes.
Ventilation
• Gasoline vapor and exhaust gas are
heavier than air and extremely poisonous. If
gasoline vapor or exhaust gas is inhaled in
large quantities, it may cause loss of con-
sciousness and death within a short time.
• When test running an engine indoors (for
example, in a water tank) make sure to do
so where adequate ventilation can be main-
tained.

0-2
Safety while working
0
1
2
3
4
5
6
7
8
9
10
A
Self-protection
• Protect your eyes by wearing safety
glasses or safety goggles during all opera-
tions involving drilling and grinding, or when
using an air compressor.
• Protect your hands and feet by wearing pro-
tective gloves and safety shoes when nec-
essary.
Working with crane
• Outboard motors weighing 18.0 kg (39.7 lb)
and over must be carried by a crane.
• Use the wire ropes of adequate strength,
and lift up the outboard motor using the
three point suspension.
• If the outboard motor does not have three
or more points to be suspended, support it
using additional ropes or the like so that the
outboard motor can be lifted and carried in
a stable manner.
Part, lubricant, and sealant
Use only genuine Yamaha parts, lubricants,
and sealants, or those recommended by
Yamaha, when servicing or repairing the out-
board motor.
Handling of sealant
• Wear protective gloves to protect your skin,
when using the sealants.
• See the material safety data sheet issued
by the manufacturer. Some of the sealants
may be harmful to human health.
Special service tool
Use the recommended special service tools
to work safely, and to protect parts from dam-
age.

0-3
GEN
INFO
General information
Tightening torque
Follow the tightening torque specifications
provided throughout the manual. When tight-
ening nuts, bolts, and screws, tighten the
large sizes first, and tighten fasteners starting
in the center and moving outward.
Non-reusable part
Always use new gaskets, seals, O-rings, cot-
ter pins, and so on, when installing or assem-
bling parts.
Disassembly and assembly
• Use compressed air to remove dust and dirt
during disassembly.
• Apply engine oil to the contact surfaces of
moving parts before assembly.
• Install bearings so that the bearing identifi-
cation mark is facing in the direction indi-
cated in the installation procedure. In
addition, make sure to lubricate the bear-
ings liberally.
• Apply a thin coat of water resistant grease
to the lip and periphery of an oil seal before
installation.
• Check that moving parts operate normally
after assembly.

0-4
How to use this manual
0
1
2
3
4
5
6
7
8
9
10
A
How to use this manual
Manual format
The format of this manual has been designed to make service procedures clear and easy to under-
stand. Use the following information as a guide for effective and quality service.
• Parts are shown and detailed in an exploded diagram and are listed in the component list (see a
in the following figure for an example page).
• The component list consists of part names and quantities, as well as bolt and screw dimensions
(see bin the following figure).
• Symbols are used to indicate important aspects of a procedure, such as the grade of lubricant and
the lubrication points (see cin the following figure).
• Tightening torque specifications are provided in the exploded diagrams (see din the following fig-
ure), and in the related detailed instructions. Some torque specifications are listed in stages as
torque figures or angles in degrees.
• Separate procedures and illustrations are used to explain the details of removal, checking, and
installation where necessary (see ein the following figure for an example page).
TIP:
For troubleshooting procedures, see Chapter 4, “Troubleshooting.”
8-1
LOWR Lower unit
Lower unit
skrameRyt’QemantraP.oN
2revoC1
6M1tlobtniojtfihS2 20 mm
1tnioJ3
1tnioJ4
1wercskcehC5
3teksaG6
1wercsgnihsulF7
2lewoD8
1niprettoC9
1tunrelleporP01
1rehsaW11
1relleporP21
1recapS31
14 Lower case mounting bolt 2 M6 40 mm
1rehsawkcoL51
6M1tloB61 20 mm
1edonA71
A
1
1
23
4
23
8
8
23
22
21
19 19
56
11 14
14
18
6
17 15
16
13
12
11 10
9
16 N·m (1.6 kgf·m, 11.8ft·lb)
15N·m (1.5 kgf·m, 11.1 ft·lb)
11N·m (1.1 kgf·m, 8.1 ft·lb)
9 N·m (0.9 kgf·m, 6.6 ft·lb)
9 N·m (0.9 kgf·m, 6.6 ft·lb)
9 N·m (0.9 kgf·m, 6.6 ft·lb)
76
20
11N·m (1.1 kgf·m, 8.1 ft·lb)
AL-transom model
8-15
LOWR Lower unit
TIP:
While turning the drive shaft clockwise, push
down on the water pump housing and install
water pump housing.
8. Install the plates mand rubber seal n.
Checkingthe lower unit for air
leakage
1. Install newgaskets a, the drain screwb
and the flushing screwc.
2. Tighten the drain screwband flushing
screwcto the specified torque.
3. Install the special service tool d.
4. Apply the specified pressure to check
that the pressure is maintained in the
lower unit for at least 10 seconds.
NOTICE: Do not over pressurize the
lower unit. Otherwise, the oil seals
could be damaged.
5. If the specified pressure cannot be
maintained, check the drive shaft,
propeller shaft, and rubber seal for bends
or damage, and check the shift rod
rubber seal for damage or wear.
Assemblingthe extension (L-
transom model)
1. Install the bushing aand circlip b.
Drain screwb:
9 N·m (0.9 kgf·m, 6.6 ft·lb)
Flushing screwc:
9 N·m (0.9 kgf·m, 6.6 ft·lb)
n
m
m
c
a
b
a
Leakage tester d: 90890-06840
Holding pressure:
98.0 kPa (0.98kgf/cm2, 14.2 psi)
Driver rod L3 c: 90890-06652
Needle bearing attachment d:
90890-06615
d
c
d
a
ac
d
b
e
b
c d a
Safety while working / How to use this manual

0-5
GEN
INFO
General information
Abbreviation
The following abbreviations are used in this service manual.
Abbreviation Description
API American Petroleum Institute
BTDC Before Top Dead Center
CCA Cold Cranking Ampere
CDI Capacitor Discharge Ignition
EN European Norm (European standard)
FForward
IEC International Electrotechnical Commission
N Neutral
OHV Overhead Valve
PORT Port side
RReverse
RON Research Octane Number
STBD Starboard side
TDC Top Dead Center

0-6
Lubricant, sealant, and thread locking agent
0
1
2
3
4
5
6
7
8
9
10
A
Lubricant, sealant, and thread locking agent
Symbol
Symbols in an exploded diagram or illustration indicate the grade of lubricant and the lubrication
points.
Symbols in an exploded diagram or illustration indicate the type of sealant or thread locking agent
and the application points.
Symbol Name Application
Yamaha 4-stroke motor oil Lubricant
Gear oil Lubricant
Water resistant grease
(Yamaha grease A)
Lubricant
Molybdenum disulfide grease Lubricant
Corrosion resistant grease
(Yamaha grease D)
Lubricant
ThreeBond 1901 Lubricant
Symbol Name Application
ThreeBond 1324 Thread locking agent
ThreeBond 1342J Thread locking agent
Gasket Maker Sealant
LOCTITE 572 (white) Sealant
How to use this manual / Lubricant, sealant, and thread locking agent

0-7
GEN
INFO
General information
Special service tool
For all markets except U.S.A. and Canada
Special service tools with Yamaha part numbers (90890-*****) are distributed by the Parts Division.
Digital circuit tester
90890-03174
Peak voltage adapter B
90890-03172
Ignition tester (spark gap tester)
90890-06754
Vacuum/pressure pump gauge set
90890-06756
Leakage tester
90890-06840
Pilot screw driver
90890-06673
Compression gauge
90890-03160
Digital tachometer
90890-06760
Timing light
90890-03141
Flywheel holder
90890-06522

0-8
Special service tool
0
1
2
3
4
5
6
7
8
9
10
A
Flywheel puller
90890-06521
Driver rod L3
90890-06652
Needle bearing attachment
90890-06615
Needle bearing attachment
90890-06613
Valve spring compressor
90890-04019
Valve spring compressor attachment
90890-06320
Valve guide remover/installer
90890-06801
Valve guide reamer
90890-06804
Valve lapper
90890-04101
Valve seat cutter holder
90890-06316

0-9
GEN
INFO
General information
Valve seat cutter 30°
90890-06818
Valve seat cutter 45°
90890-06312
Valve seat cutter 60°
90890-06323
Valve seat cutter 30°
90890-06819
Valve seat cutter 45°
90890-06814
Valve seat cutter 60°
90890-06813
Needle bearing attachment
90890-06612
Driver rod LL
90890-06605
Ball bearing attachment
90890-06632
Driver rod LS
90890-06606

0-10
Special service tool
0
1
2
3
4
5
6
7
8
9
10
A
Ball bearing attachment
90890-06655
Piston slider
90890-06529
Stopper guide plate
90890-06501
Stopper guide stand
90890-06538
Bearing puller assembly
90890-06535
Bearing outer race attachment
90890-06628
Bushing installer center bolt
90890-06601
Bushing attachment
90890-06650
Bushing attachment
90890-06649

0-11
GEN
INFO
General information
— MEMO —

SPEC
0
1
2
3
4
5
6
7
8
9
10
A
Specification 1
Model feature ..................................................................... 1-1
General feature ......................................................................... 1-1
Model designation ..................................................................... 1-2
Serial number ............................................................................ 1-2
Model data ......................................................................... 1-3
Dimension and weight ............................................................... 1-3
Performance .............................................................................. 1-3
Power unit ................................................................................. 1-3
Lower unit .................................................................................. 1-4
Bracket unit ............................................................................... 1-4
Fuel and oil requirement ............................................................ 1-4
Electrical technical data ................................................... 1-5
Ignition timing control system .................................................... 1-5
Charging system (optional for European market) ...................... 1-5
Fuel system technical data .............................................. 1-5
Fuel system ............................................................................... 1-5
Power unit technical data ................................................. 1-6
Power unit ................................................................................. 1-6
Manual starter ........................................................................... 1-6
Cylinder head assembly ............................................................ 1-7
Crankcase assembly ................................................................. 1-8
Lower unit technical data ................................................. 1-9
Lower unit assembly .................................................................. 1-9
Specified tightening torque ............................................ 1-10
Fuel system ............................................................................. 1-10
Power unit ............................................................................... 1-10
Lower unit ................................................................................ 1-10
Bracket unit ............................................................................. 1-11
General tightening torque .............................................. 1-11

1-1
SPEC
Specification
Model feature
General feature
F4B, F5A, F6C Overall feature
• 4-stroke, 1-cylinder, OHV, 2-valve, 139.0 cm3(8.5 cu. in) engine
• Low emission in compliance with EU regulations
aPower unit
• Compact OHV engine
• Blowby gas reburning system
• Trochoid type oil pump lubrication
• Decompression starter
• Fuel line with a primer pump
• Dual fuel line
• Recoil manual starter
bElectrical
• Ignition timing control by CDI unit
• CDI unit with the integrated ignition coil
• Charging system (optional for European
market)
cBracket unit
• Manual tilt
• Reverse lock system
• Balanced carrying handle
dLower unit
• Under water exhaust system
a
b
c
d

1-2
Model feature
0
1
2
3
4
5
6
7
8
9
10
A
Model designation
Serial number
The outboard motor serial number is indi-
cated on a label affixed to the port clamp
bracket.
aModel name
bApproved model code
cTransom height
dSerial number
eProduction model year
aModel description F: 4-stroke regular rotation
bModel name 4: 4/5/6
cProduct generation B: A and up
dFunctions M: Manual starter
eH: Tiller handle
fTransom height S: S (15 in)
L: L (20 in)
F 4 B M H S
bacdef
M B K INDUSTRIE
PRODUCT ASSEMBLED IN FRANCE
PRODUIT ASSEMBLE EN FRANCE
b
ca
d
e
Model name Approved
model code
Starting
serial No.
F4BMH 6EC 1000001–
F5AMH 6ED 1000001–
F6CMH 6EE 1000001–

1-3
SPEC
Specification
Model data
Dimension and weight
Performance
Power unit
Item Unit Model
F4BMH F5AMH F6CMH
Overall length mm (in) 750.0 (29.5)
Overall width mm (in) 403.0 (15.9)
Overall height
Smm(in)
1040.0 (40.9)
Lmm(in)
1168.0 (46.0)
Boat transom height
Smm(in)
440.0 (17.3)
Lmm(in)
568.0 (22.4)
Weight (with propeller)
S kg (lb) 27.0 (59.5)
L kg (lb) 28.0 (61.7)
Item Unit Model
F4BMH F5AMH F6CMH
Maximum output
At 5000 r/min kW (HP) 2.9 (3.9) —
At 5500 r/min kW (HP) — 3.7 (5.0) 4.4 (6.0)
Full throttle operating range r/min 4000–5000 4500–5500
Engine idle speed r/min 1450–1550
Item Unit Model
F4BMH F5AMH F6CMH
Type 4-stroke, OHV
Cylinder quantity 1
Total displacement cm³ (cu. in) 139.0 (8.5)
Bore stroke mm (in) 62.0 46.0 (2.4 1.8)
Compression ratio 8.90 : 1
Control system Tiller handle
Starting system Manual
Fuel system Carburetor
Ignition control system CDI
Advance type Microcomputer
Starting enrichment Choke valve
Spark plug CR6HSB (NGK)
Cooling system Water
Exhaust system Under water
Lubrication system Wet sump