Yamaha EK25BMH User manual

290404
EK25BMH
69T-28197-ZA-11
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NOTICE
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 equip-
ment. It has been written to suit the needs of persons who have a 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 edi-
tion of this manual. Authorized Yamaha dealers are notified periodically of modifications and
significant changes in specifications and procedures, and these are incorporated in succes-
sive editions of this manual.
EK25BMH
SERVICE MANUAL
©2000 Yamaha Motor Co., Ltd.
1st Edition, October 2000
All rights reserved. Any reprinting or
unauthorized use without the written
permission of Yamaha Motor Co., Ltd.
is expressly prohibited.
Printed in Japan

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HOW TO USE THIS MANUAL
MANUAL FORMAT
All of the procedures in this manual are organised in a sequential, step-by-step format. The
information has been compiled to provide the mechanic with an easy to read, handy refer-
ence that contains comprehensive explanations of all disassembly, repair, assembly, and
inspection operations.
In this revised format, the condition of a faulty component will precede an arrow symbol and
the course of action required will follow the symbol, e.g.,
• Bearings
Pitting/scratches →Replace.
To assist you in finding your way through this manual, the section title and major heading is
given at the top of every page.
MODEL INDICATION
Multiple models are referred to in this manual and their model indications are noted as fol-
lows.
ILLUSTRATIONS
The illustrations within this service manual represent all of the designated models.
CROSS REFERENCES
The cross references have been kept to a minimum. Cross references will direct you to the
appropriate section or chapter.
Model name EK25BMH
Indication EK25BMH

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IMPORTANT INFORMATION
In this Service Manual particularly important information is distinguished in the following
ways.
The safety Alert Symbol means ATTENTION! BECOME ALERT! YOUR SAFETY IS
INVOLVED!
WARNING
Failure to follow WARNING instructions could result in severe injury or death to the machine
operator, a bystander or a person inspecting or repairing the outboard motor.
CAUTION:
A CAUTION indicates special precautions that must be taken to avoid damage to the out-
board motor.
NOTE:
A NOTE provides key information to make procedures easier or clearer.

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HOW TO USE THIS MANUAL
1
The main points regarding removing/installing and disassembling/assembling proce-
dures are shown in the exploded views.
2
The numbers in the exploded views indicate the required sequence of the procedure and
should be observed accordingly.
3
Symbols are used in the exploded views to indicate important aspects of the procedure.
A list of meanings for these symbols is provided on the following page.
4
It is important to refer to the job instruction charts at the same time as the exploded views .
These charts list the sequence that the procedures should be carried out in, as well as
providing explanations on part names, quantities, dimensions and important points relat-
ing to each relevant task.
5
In addition to tightening torques, the dimensions of the bolts and screws are also men-
tioned.
Example:
Bolt and screw size 10 × 25 mm : bolt and screw diameter (D) × lenght (L)
6
In addition to the exploded views and job instruction charts, this manual provides indi-
vidual illustrations when further explanations are required to explain the relevant proce-
dure.
1
2
3
4
2
5
6

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SYMBOLS
Symbols to are designed as thumb-
tabs to indicate the content of a chapter.
1
General information
2
Specifications
3
Periodic check and adjustments
4
Fuel system
5
Power unit
6
Lower unit
7
Bracket unit
8
Electrical systems
9
Trouble analysis
Symbols to indicate specific data.
10
Special tool
11
Specified liquid
12
Specified engine speed
13
Specified torque
14
Specified measurement
15
Specified electrical value
[Resistance (Ω), Voltage (V), Electric current
(A)]
Symbol to in an exploded diagram
indicate the grade of lubricant and the loca-
tion of the lubrication point.
16
Apply Yamaha 2-stroke motor oil
17
Apply water resistant grease
(Yamaha grease A, Yamaha marine grease)
18
Apply water resistant grease
(Yamaha grease C, Yamaha marine grease)
19
Apply water resistant grease
(Yamaha grease D, Yamaha marine grease)
20
Apply molybdenum disulfide grease
Symbols to in an exploded dia-
gram indicate the grade of the sealing or
locking agent and the location of the appli-
cation point.
21
Apply Gasket Maker®
22
Apply Yamabond #4
(Yamaha bond number 4)
23
Apply LOCTITE®No.271 (Red LOCTITE)
24
Apply LOCTITE®No.242 (Blue LOCTITE)
25
Apply LOCTITE®No.572
26
Apply silicon sealant
1 2
3 4
5 6
7 8
910
11 12
13 14
15 16
17 18
19 20
21 22
23 24
25 26
GEN
INFO SPEC
CHK
ADJ FUEL
POWR LOWR
BRKT –+
ELEC
TRBL
ANLS
T
R
.
.
E
AC
DM
GM 4
271
LT
242
LT
572
LT LT
SS
1 9
10 15
16 20
21 26

–+
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1
2
3
4
5
6
7
8
9
CONTENTS
GEN
INFO
SPEC
CHK
ADJ
FUEL
POWR
LOWR
BRKT
ELEC
TRBL
ANLS
GENERAL INFORMATION
SPECIFICATIONS
PERIODIC CHECK AND
ADJUSTMENT
FUEL SYSTEM
RECOIL STARTER
LOWER UNIT
BRACKET UNIT
ELECTRICAL SYSTEM
TROUBLE ANALYSIS

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1
2
3
4
5
6
7
8
9
GEN
INFO
CHAPTER 1
GENERAL INFORMATION
IDENTIFICATION ............................................................................................ 1-1
SERIAL NUMBER .................................................................................... 1-1
STARTING SERIAL NUMBERS ............................................................... 1-1
SAFETY WHILE WORKING ........................................................................... 1-2
FIRE PREVENTION .................................................................................. 1-2
VENTILATION .......................................................................................... 1-2
SELF-PROTECTION ................................................................................. 1-2
OILS, GREASES AND SEALING FLUIDS ............................................... 1-2
GOOD WORKING PRACTICES ............................................................... 1-3
DISASSEMBLY AND ASSEMBLY ........................................................... 1-4
SPECIAL TOOLS ............................................................................................ 1-5
MEASURING ........................................................................................... 1-5
REMOVING AND INSTALLING ............................................................... 1-7
FEATURES AND BENEFITS ........................................................................... 1-9
POWER UNIT ........................................................................................... 1-9
IGNITION SYSTEM ............................................................................... 1-10
COOLING SYSTEM ................................................................................1-11
TILLER HANDLE .................................................................................... 1-13
BRACKET AND BOTTOM COWLING ................................................... 1-14

IDENTIFICATION
GEN
INFO
1-1
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1
IDENTIFICATION
SERIAL NUMBER
The outboard motor’s serial number is
stamped on a label which is attached to the
port clamp bracket.
NOTE:
As an antitheft measure, a special label on
which the outboard motor’s serial number
is stamped is bonded to the port clamp
bracket. The label is specially treated so
that peeling it off causes cracks across the
serial number.
1
Model name
2
Approval model code
3
Transom height
4
Serial number
STARTING SERIAL NUMBERS
The starting serial number blocks are as fol-
lows:
Model name Approval
model code
Starting serial
number
Worldwide
EK25BMH 62C
S:10 0101
L:400101
Y:750101

SAFETY WHILE WORKING
1-2
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GEN
INFO
SAFETY WHILE WORKING
The procedures given in this manual are
those recommended by Yamaha to be fol-
lowed by Yamaha dealers and their
mechanics.
FIRE PREVENTION
Gasoline (petrol) is highly flammable.
Petroleum vapor is explosive if ignited.
Do not smoke while handling gasoline and
keep it away from heat, sparks and open
flames.
VENTILATION
Petroleum vapor is heavier than air and is
deadly if inhaled in large quantities. Engine
exhaust gases are harmful to breathe.
When test-running an engine indoors,
maintain good ventilation.
SELF-PROTECTION
Protect your eyes with suitable safety
glasses or safety goggles, when grinding or
when doing any operation which may cause
particles to fly off. Protect hands and feet by
wearing safety gloves or protective shoes if
appropriate to the work you are doing.
OILS, GREASES AND SEALING
FLUIDS
Use only genuine Yamaha oils, greases and
sealing fluids or those recommended by
Yamah a.

SAFETY WHILE WORKING
GEN
INFO
1-3
E
Under normal conditions or use, there
should be no hazards from the use of the
lubricants mentioned in this manual, but
safety is all-important, and by adopting
good safety practices, any risk is minimized.
A summary of the most important precau-
tions is as follows:
1. While working, maintain good stan-
dards of personal and industrial
hygiene.
2. Clothing which has become contami-
nated with lubricants should be
changed as soon as practicable, and
laundered before further use.
3. Avoid skin contact with lubricants; do
not, for example, place a soiled wiping-
rag in your pocket.
4. Hands and any other part of the body
which have been in contact with lubri-
cants or lubricant-contaminated cloth-
ing, should be thoroughly washed with
hot water and soap as soon as practica-
ble.
5. To protect the skin, the application of a
suitable barrier cream to the hands
before working, is recommended.
6. A supply of clean lint-free cloths should
be available for wiping purposes.
GOOD WORKING PRACTICES
1. The right tools
Use the recommended special tools to
protect parts from damage. Use the
right tool in the right manner - do not
improvise.
2. Tightening torque
Follow the tightening torque instruc-
tions. When tightening bolts, nuts and
screws, tighten the large sizes first, and
tighten inner-positioned fixings before
outer-positioned ones.

SAFETY WHILE WORKING
1-4
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GEN
INFO
3. Non-reusable items
Always use new gaskets, packings, O-
rings, split-pins, circlips, etc., on reas-
sembly.
DISASSEMBLY AND ASSEMBLY
1. Clean parts with compressed air when
disassembling.
2. Oil the contact surfaces of moving parts
before assembly.
3. After assembly, check that moving parts
operate normally.
4. Install bearings with the manufacturer’s
markings on the side exposed to view,
and liberally oil the bearings.
5. When installing oil seals, apply a light
coating of water-resistant grease to the
outside diameter.

SPECIAL TOOLS
GEN
INFO
1-5
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SPECIAL TOOLS
Using the correct special tools recom-
mended by Yamaha, will aid the work and
enable accurate assembly and tune-up.
Improvising and using improper tools can
damage the equipment.
MEASURING
1
Dial gauge set
P/N. 90890-01252
2
Crank stand alignment
P/N. 90890-03107
3
Pocket tester
P/N. 90890-03112
4
Timing light
P/N. 90890-03141
5
Compression Gauge
P/N. 90890-03160
6
Peak voltage adaptor
P/N. 90890-03172
7
Digital circuit tester
P/N. 90890-03174
8
Ignition tester
P/N. 90890-06754
9
Vacuum/pressure pump gauge set
P/N. 90890-06756
10
Digital tachometer
P/N. 90890-06760
11
Leakage tester
P/N. 90890-06762
12
Digital caliper
P/N. 90890-06704
1 2
3 4
5 6
7 8
910
11 12

SPECIAL TOOLS
1-6
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GEN
INFO
13
Cylinder gauge
P/N. 90890-06759
14
Outside micrometer
P/N. 90890-03006
P/N. 90890-03008
15
Inside micrometer
P/N. 90890-03010
16
Thickness gauge
P/N. 90890-03079
17
Shimming plate
P/N. 90890-06701
18
Pinion height gauge
P/N. 90890-06702
19
Magnet base
P/N. 90890-06705
20
Backlash indicator
P/N. 90890-06706
21
Magnet base plate
P/N. 90890-07003
13 14
15 16
17 18
19 20
21

SPECIAL TOOLS
GEN
INFO
1-7
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REMOVING AND INSTALLING
1
Flywheel puller
P/N. 90890-06521
2
Flywheel holder
P/N. 90890-06522
3
Small end bearing installer
P/N. 90890-06527
4
Bearing separator
P/N. 90890-06534
5
Stopper guide plate
P/N. 90890-06501
6
Bearing housing puller claw
P/N. 90890-06564
7
Center bolt
P/N. 90890-06504
8
Drive shaft holder 3
P/N. 90890-06517
9
Bearing puller ass’y
P/N. 90890-06535
10
Stopper guide stand
P/N. 90890-06538
11
Driver rod LL
P/N. 90890-06605
12
Driver rod LS
P/N. 90890-06606
13
Driver rod L3
P/N. 90890-06652
14
Driver rod SL
P/N. 90890-06602
15
Driver rod SS
P/N. 90890-06604
16
Bearing depth plate
P/N. 90890-06603
17
Needle bearing attachment
P/N. 90890-06608
P/N. 90890-06611
P/N. 90890-06615
18
Ball bearing attachment
P/N. 90890-06633
19
Bearing inner race attachment
P/N. 90890-06643
P/N. 90890-06644
P/N. 90890-06645
20
Bearing outer race attachment
P/N. 90890-06622
P/N. 90890-06628
1 2
3 4
5 6
7 8
910
11 12
13 14
15 16
17 18
19 20

SPECIAL TOOLS
1-8
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GEN
INFO
Crank jig ass’y
P/N. 90890-02421
21
Frange
P/N. 90890-02351
22
Body
P/N. 90890-02352
23
Bolt
P/N. 90890-02353
24
Washer
P/N. 90890-02354
25
Bushing-5 (D25)
P/N. 90890-02359
26
Bushing-12 (D35)
P/N. 90890-02366
27
Height ring-13 (H57)
P/N. 90890-02379
28
Pressure Plate
P/N. 90890-02384
29
Press body
P/N. 90890-02385
30
Plate A
P/N. 90890-02386
31
Plate B
P/N. 90890-02387
32
Pressure pin B
P/N. 90890-02390
33
Bearing pressure B
P/N. 90890-02392
34
Bearing pressure C
P/N. 90890-02393
35
Support
P/N. 90890-02394
36
Spacer B
P/N. 90890-02396
37
Bushing-14
P/N. 90890-02419
21 22
23 24
25 26
27 28
29 30
31 32
33 34
35 36
37

FEATURES AND BENEFITS
GEN
INFO
1-9
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FEATURES AND BENEFITS
POWER UNIT
The EK25B is designed to provide superior fuel economy, serviceability, and durability.
They are based on the previous EK25A with newly designed linkage to control both throttle
opening and ignition timing mechanically and simultaneously.
Special attention was paid on the crankshaft bearings. Collar is now added to the upper main
journal of the crankshaft. Roller bearing is applied for the center bearing.
The collar added on the upper main journal contributes to get and better serviceability.
Fig. 2
Fig. 1

FEATURES AND BENEFITS
1-10
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GEN
INFO
IGNITION SYSTEM
Ignition system on the EK25B consists of flywheel magnet, charge coil, pulser coil, CDI unit,
and ignition coil.
Similar to the previous EK25A, the engine has the mechanical ignition timing advance system
that works by way of the linkage.
Superior fuel economy is attained by the modified ignition timing control arrangement.
Also the system restricts the ignition timing advance to prevent engine kickback when the
shift is in neutral.
Fig. 3

FEATURES AND BENEFITS
GEN
INFO
1-11
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COOLING SYSTEM
New structure applied to the cooling system provides additional cooling capacity in the upper
casing.
With additional cooling water passage (indicated by ), water walls contained in the new
upper casing contribute to the reduction of outer surface temperature.
Fig. 4