Yanmar 6LY3 series User manual

6LY3
series
6LY3 Service Manual
SERVICE MANUAL
P/N: 0BLY3-U00100
MARINE
ENGINES

ii 6LY3 Service Manual
© 2007 Yanmar Marine International
This Service Manual has been developed for the exclusive use of service and repair professionals such as
Yanmar authorized distributors and Yanmar authorized dealers. It is written with these professionals in mind
and may not contain the necessary detail or safety statements that may be required for a non-professional to
perform the service or repair properly and / or safely. Please contact an authorized Yanmar repair or service
professional before working on your Yanmar product.
Disclaimers:
All information, illustrations and specifications in this manual are based on the latest information available at
the time of publishing. The illustrations used in this manual are intended as representative reference views
only. Moreover, because of our continuous product improvement policy, we may modify information,
illustrations, and / or specifications to explain and / or exemplify a product, service or maintenance
improvement. We reserve the right to make any change at any time.
Yanmar and are registered trademarks of Yanmar Co., Ltd. in Japan, the United States and / or
other countries.
All Rights Reserved:
No part of this publication may be reproduced or used in any form, by any means - graphic, electronic, or
mechanical, including photocopying, recording, taping, or information storage and retrieval systems - without
the written permission of Yanmar Marine International.
© 2007 Yanmar Marine International.
1107

6LY3 Service Manual iii
© 2007 Yanmar Marine International
TABLE OF
CONTENTS
Page
Introduction ......................................................................................... 1-1
Safety.................................................................................................... 2-1
General Service Information .............................................................. 3-1
Periodic Maintenance ......................................................................... 4-1
Engine .................................................................................................. 5-1
Fuel System ......................................................................................... 6-1
Coolant System ................................................................................... 7-1
Lubrication .......................................................................................... 8-1
Turbocharger....................................................................................... 9-1
Starter................................................................................................. 10-1
Alternator ........................................................................................... 11-1
Electrical and ECU ............................................................................ 12-1
Troubleshooting................................................................................ 13-1
Service Standards............................................................................. 14-1

TABLE OF CONTENTS
iv 6LY3 Service Manual
© 2007 Yanmar Marine International
This Page Intentionally Left Blank

6LY3 Service Manual 1-1
© 2007 Yanmar Marine International
6LY3 Service Manual Section 1
INTRODUCTION
This manual gives specific instructions for the
proper repair of Yanmar 6LY3 series marine
engines.
Please follow the procedures carefully to ensure
quality service.
Yanmar recommends reading this Service Manual
completely before starting with repairs.
Along with standard tools, Yanmar recommends the
use of special tools necessary to perform repairs
correctly.
Yanmar products are continuously undergoing
improvement. This Service Manual has been
checked carefully in order to avoid errors. However,
Yanmar is not liable for any misrepresentations,
errors of description or omissions. Contact your
authorized Yanmar marine dealer or distributor for
any questions you have regarding this Service
Manual.

INTRODUCTION Revision History
1-2 6LY3 Service Manual
© 2007 Yanmar Marine International
REVISION HISTORY
This manual is a living document. Periodic manual
revisions are published to document product
improvements and changes. This practice ensures
the manual has the most current information.
As manual revisions become necessary, individual
pages are prepared and sent to those who need
the information. If a page or number of pages
should be replaced, the replacement information is
sent along with a revised Revision Control Table.
Discard the older, obsolete information.
At times, the revision involves inserting additional
pages in one or more sections. Replace the
Revision Control Table and insert the new pages.
This method of revision control represents the most
cost-effective solution to providing current, updated
information as needed.
Revision Control Table
Revision Date
Revision Number
New Page Numbers
Involved Remarks Initiating
Department
Aug. 2007
Rev. 0 ALL Initial Release YMI

6LY3 Service Manual 2-1
© 2007 Yanmar Marine International
6LY3 Service Manual Section 2
SAFETY
SAFETY STATEMENTS
Yanmar is concerned for your safety and the
condition of your marine engine. Safety statements
are one of the primary ways to call your attention to
the potential hazards associated with Yanmar
marine engines. Follow the precautions listed
throughout the manual before operation, during
operation and during periodic maintenance
procedures for your safety, the safety of others and
to protect the performance of your marine engine.
Keep the decals from becoming dirty or torn and
replace them if they are lost or damaged. Also, if a
part needs to be replaced that has a decal attached
to it, make sure to order the new part and decal at
the same time.
Indicates a hazardous situation which, if not
avoided, will result in death or serious injury.
Indicates a hazardous situation which, if not
avoided, could result in death or serious injury.
Indicates a hazardous situation which, if not
avoided, could result in minor or moderate
injury.
Indicates a situation which can cause damage to
the engine, personal property and / or the
environment or cause the equipment to operate
improperly.
A
This safety alert symbol appears
with most safety statements. It
means attention, become alert,
your safety is involved! Please read
and abide by the message that
follows the safety alert symbol.

SAFETY Safety Precautions
2-2 6LY3 Service Manual
© 2007 Yanmar Marine International
SAFETY PRECAUTIONS
There is no substitute for common sense and
careful practices. Improper practices or
carelessness can cause burns, cuts, mutilation,
asphyxiation, other bodily injury or death. This
information contains general safety precautions
and guidelines that must be followed to reduce risk
to personal safety. Special safety precautions are
listed in specific procedures. Read and understand
all of the safety precautions before operating,
performing repairs or maintenance.
The safety messages that follow have DANGER
level hazards. These safety messages describe
a hazardous situation which, if not avoided, will
result in death or serious injury.
NEVER permit anyone to install or
operate the engine without proper
training.
• Read and understand this Service Manual before
operating or servicing the engine to ensure that
safe operating practices and maintenance
procedures are followed.
• Safety signs and decals are additional reminders
for safe operating and maintenance techniques.
• See your authorized Yanmar marine dealer or
distributor for additional training.
Crush Hazard
NEVER stand under a hoisted
engine. If the hoist mechanism fails,
the engine will fall on you.
ALWAYS secure the engine solidly to prevent the
engine from falling during maintenance.
The safety messages that follow have
WARNING level hazards. These safety
messages describe a hazardous situation
which, if not avoided, could result in death or
serious injury.
Explosion Hazard
While the engine is running or the
battery is charging, hydrogen gas is
being produced and can be easily
ignited. Keep the area around the
battery well-ventilated and keep sparks,
open flame and any other form of ignition out of the
area.
ALWAYS turn off the battery switch (if equipped) or
disconnect the negative (-) battery cable before
servicing the equipment.
Fire and Explosion Hazard
Diesel fuel is flammable and explosive
under certain conditions.
NEVER use a shop rag to catch the fuel.
Wipe up all spills immediately.
NEVER refuel with the engine running.
Store any containers containing fuel in a
well-ventilated area, away from any combustibles or
sources of ignition.

SAFETY
Safety Precautions
12/05
6LY3 Service Manual 2-3
© 2007 Yanmar Marine International
Fire Hazard
Have appropriate safety equipment
available. Have all fire extinguishers
checked periodically for proper
operation and / or readiness.
ALWAYS read and follow safety-related precautions
found on containers of hazardous substances like
parts cleaners, primers, sealants and sealant
removers.
Undersized wiring systems can cause an electrical
fire.
Entanglement Hazard
NEVER leave the key in the key switch
when servicing the engine. Attach a
“Do Not Operate” tag near the key
switch while performing maintenance
on the equipment.
ALWAYS stop the engine before beginning service.
If the engine must be serviced while it is operating,
remove all jewelry, tie back long hair and keep
hands, other body parts and clothing away from
moving / rotating parts.
Piercing Hazard
Avoid skin contact with high-pressure
diesel fuel spray caused by a fuel
system leak such as a broken fuel
injection line. High-pressure fuel can
penetrate your skin and result in
serious injury. If you are exposed to high-pressure
fuel spray, obtain prompt medical treatment.
NEVER check for a fuel leak with your hands.
ALWAYS use a piece of wood or cardboard. Have
your authorized Yanmar marine dealer or distributor
repair the damage.
Flying Object Hazard
ALWAYS wear eye protection when servicing the
engine or when using compressed air or
high-pressure water. Dust, flying debris,
compressed air, pressurized water or steam may
injure your eyes.
Coolant Hazard
Wear eye protection and rubber gloves
when handling Long Life Coolant (LLC).
If contact with the eyes or skin should
occur, flush eyes and wash immediately with clean
water.

SAFETY Safety Precautions
2-4 6LY3 Service Manual
© 2007 Yanmar Marine International
Sever Hazard
NEVER wear jewelry, unbuttoned
cuffs, ties or loose-fitting clothing and
ALWAYS tie long hair back when
working near moving / rotating parts
such as the flywheel or PTO shaft. Keep hands,
feet and tools away from all moving parts.
The propeller may rotate during towing or if the
engine is running at idle speed. NEVER service the
engine while being towed or when the engine is
running.
If the vessel has more than one engine, NEVER
service an engine if either of the engines is running.
In multi-engine configurations the propeller for an
engine that is shut down may rotate if any of the
other engines are running.
Electrical Hazard
Make welding repairs safely.
• ALWAYS turn off the battery switch (if
equipped) or disconnect the negative
(-) battery cable and the leads to the
alternator when welding on the
equipment.
• Remove the multi-pin connector to the engine
control unit. Connect the weld clamp to the
component to be welded and as close as possible
to the welding point.
• NEVER connect the weld clamp to the engine or
in a manner which would allow current to pass
through a mounting bracket.
• When welding is complete, reconnect the leads to
the alternator and engine control unit prior to
reconnecting the batteries.
ALWAYS keep the electrical connectors and
terminals clean. Check the electrical harnesses for
cracks, abrasions and damaged or corroded
connectors.
NEVER turn off the battery switch (if equipped) or
short the battery cables during operation. Damage
to the electrical system will result.
Exhaust Hazard
All internal combustion engines create
carbon monoxide gas during operation
and special precautions are required to
avoid carbon monoxide poisoning.
• NEVER block windows, vents or other means of
ventilation if the engine is operating in an
enclosed area.
• ALWAYS ensure that all connections are
tightened to specifications after repair is made to
the exhaust system.
Burn Hazard
Some of the engine surfaces become
very hot during operation and shortly
after shutdown.
• Keep hands and other body parts away from hot
engine surfaces.
• Handle hot components with heat-resistant
gloves.

SAFETY
Safety Precautions
12/05
6LY3 Service Manual 2-5
© 2007 Yanmar Marine International
Sudden Movement Hazard
The engine lifting eyes are engineered to lift the
weight of the marine engine only. ALWAYS use the
engine lifting eyes when lifting the engine.
Lifting Hazard
Additional equipment is necessary to lift the marine
engine and marine gear together. ALWAYS use
lifting equipment with sufficient capacity to lift the
marine engine.
If transport is needed for engine repair, have a
helper assist in attaching it to a hoist and loading it
onto a truck.
Alcohol and Drug Hazard
NEVER operate the engine while
under the influence of alcohol, drugs or
when ill.
Exposure Hazard
ALWAYS wear personal protective
equipment including appropriate
clothing, gloves, work shoes, eye and
hearing protection as required by the
task at hand.
Tool Hazard
ALWAYS remove any tools or shop rags used
during maintenance from the area before operation.
The safety messages that follow have CAUTION
level hazards. These safety messages describe
a hazardous situation which, if not avoided,
could result in minor or moderate injury.
ALWAYS wear eye protection when
servicing the engine or when using
compressed air or high-pressure water.
Dust, flying debris, compressed air,
pressurized water or steam may injure
your eyes.
Poor Lighting Hazard
Ensure that the work area is adequately
illuminated. ALWAYS install wire cages on portable
safety lamps.
Tool Hazard
ALWAYS use tools appropriate for the task at hand
and use the correct size tool for loosening or
tightening machine parts.

SAFETY Safety Precautions
2-6 6LY3 Service Manual
© 2007 Yanmar Marine International
The safety messages that follow have NOTICE
level hazards.
Any part which is found defective as a result of
inspection or any part whose measured value does
not satisfy the standard or limit must be replaced.
ALWAYS tighten components to the specified
torque. Loose parts can cause equipment damage
or cause it to operate improperly.
Only use replacement parts specified. Other
replacement parts may affect warranty coverage.
NEVER attempt to modify the engine design or
safety features such as defeating the engine speed
limit control or the diesel fuel injection quantity
control.
NEVER attempt to adjust the low or high idle speed
limit bolt. This may impair the safety and
performance of the engine and shorten its life.
Modifications of this type may void the warranty. If
adjustment is ever required, contact your
authorized Yanmar marine dealer or distributor.
Modifications may impair the engine’s safety and
performance characteristics and shorten the
engine’s life. Any alterations to this engine may void
its warranty. Be sure to use Yanmar genuine
replacement parts.
Follow the guidelines of the EPA or
other governmental agencies for the
proper disposal of hazardous materials
such as engine oil, diesel fuel and
engine coolant. Consult the local
authorities or reclamation facility.
NEVER dispose of hazardous materials by
dumping them into a sewer, on the ground or into
groundwater or waterways.
If any indicator illuminates during engine operation,
stop the engine immediately. Determine the cause
and repair the problem before continuing to operate
the engine.
Make sure the engine is installed on a level surface.
If a Yanmar Marine engine is installed at an angle
that exceeds the specifications stated in the
Yanmar Marine Installation Manuals, engine oil may
enter the combustion chamber causing excessive
engine speed, white exhaust smoke and serious
engine damage. This applies to engines that run
continuously or those that run for short periods of
time.

SAFETY
Location of Safety Decals
12/05
6LY3 Service Manual 2-7
© 2007 Yanmar Marine International
LOCATION OF SAFETY DECALS
Figure 2-1 shows the location of safety decals on Yanmar 6LY3 series marine engines.
Figure 2-1
Figure 2-1
1 – Part Number: 128296-07300
2 – Part Number: 120324-07240
3 – Part Number: 119773-07280
4 – Part Number: 128296-07260
5 – Part Number: 128296-07350
6 – Part Number: 119578-07890
E
003025-02E
DO NOT STEP
ON COVERS.
POSSIBILITY
OF A FALL
(1)
(2)
(3)
(4)
(5)
(6)
0006329
DO NOT STEP
ON COVERS.
POSSIBILITY
OF A FALL
LOW
FULL
NEVER pour the
engine oil across
the full line.
119773-07280

SAFETY Location of Safety Decals
2-8 6LY3 Service Manual
© 2007 Yanmar Marine International
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6LY3 Service Manual 3-1
© 2007 Yanmar Marine International
6LY3 Service Manual Section 3
GENERAL SERVICE
INFORMATION
Page
Safety Precautions .......................................................................... 3-3
6LY3-ETP Exterior Views................................................................ 3-4
Operation Side........................................................................... 3-4
Non-Operation Side................................................................... 3-4
Diesel Fuel ...................................................................................... 3-6
Diesel Fuel Specifications ......................................................... 3-6
Engine Oil........................................................................................ 3-8
Engine Oil Specifications........................................................... 3-8
Marine Gear Oil ............................................................................... 3-8
Engine Coolant................................................................................ 3-9
Handling of Coolant ................................................................... 3-9
Engine Outline Drawings............................................................... 3-10
6LY3-ETP / STP / UTP (YT-15 MOUNT) ................................ 3-10
6LY3-ETP................................................................................ 3-11
Exhaust Gas Emission Regulations .............................................. 3-12
Engine Identification ................................................................ 3-12
EPA Exhaust Gas Emission Standard..................................... 3-13
EPA Guarantee Conditions for Emission Standard ................. 3-13
Engine Nameplate......................................................................... 3-14
Reduction and Reversing Gear ..................................................... 3-14
Principal Engine Specifications ..................................................... 3-15
Abbreviations and Symbols........................................................... 3-16
Abbreviations........................................................................... 3-16
Symbols................................................................................... 3-16

GENERAL SERVICE INFORMATION
3-2 6LY3 Service Manual
© 2007 Yanmar Marine International
Unit Conversions........................................................................... 3-17
Unit Prefixes ............................................................................ 3-17
Units of Length ........................................................................ 3-17
Units of Volume ....................................................................... 3-17
Units of Mass........................................................................... 3-17
Units of Force .......................................................................... 3-17
Units of Torque........................................................................ 3-17
Units of Pressure..................................................................... 3-17
Units of Power ......................................................................... 3-17
Units of Temperature............................................................... 3-17

GENERAL SERVICE INFORMATION
Safety Precautions
12/05
6LY3 Service Manual 3-3
© 2007 Yanmar Marine International
SAFETY PRECAUTIONS
Before servicing the engine review the Safety Section on page 2-1.

GENERAL SERVICE INFORMATION 6LY3-ETP Exterior Views
3-4 6LY3 Service Manual
© 2007 Yanmar Marine International
6LY3-ETP EXTERIOR VIEWS
Operation Side
Figure 3-1
Figure 3-1
Non-Operation Side
Figure 3-2
Figure 3-2
0006254
(3)
(4)
(5)(6)(7)
(8)
(9)
(1)
(2)
0006255
(11)
(10)
(17)
(16)
(15) (14) (13)
(12)

GENERAL SERVICE INFORMATION
6LY3-ETP Exterior Views
12/05
6LY3 Service Manual 3-5
© 2007 Yanmar Marine International
1 – Filler Cap
2 – Electrical Control Unit Cover
3 – Fuel Injection Pump
4 – Oil Cooler
5 – Oil Filter
6 – Intercooler
7 – Flywheel
8 – Air Silencer
9 – Turbocharger
10 – Coolant Tank (Exhaust Manifold)
11 – Dipstick
12–HeatExchanger
13–SeawaterPump
14–Alternator
15–V-Belt
16 – Fuel Filter
17–CoolantPump

GENERAL SERVICE INFORMATION Diesel Fuel
3-6 6LY3 Service Manual
© 2007 Yanmar Marine International
DIESEL FUEL
Diesel Fuel Specifications
NOTICE: Use the correct fuel type to maintain
engine performance and reduce engine wear and
ensure compliance with emission regulations.
Fuel Selection
Diesel fuel should comply with the following
specifications:
• The fuel specifications need to comply with
national and international standards.
• ASTM D975 No. 1-D
No. 2-D for USA
• EN590: 96 for EU
• ISO 8217 DMX International
• BS 2869-A1 or A2 for UK
• JIS K2204-2 for JAPAN
Additional Fuel Requirements
• Fuel cetane number should equal 45 or higher.
• Sulfur content should not exceed 0.5% by
volume. (Preferably it should be below 0.05%.)
• Water and sediment in the diesel fuel should not
exceed 0.05% by volume.
• Ash should not exceed 0.01% by mass.
• Carbon residue content of the diesel fuel should
not exceed 0.35% by volume. (Preferably it
should be below 0.1%.)
• Total aromatic content of the diesel fuel should
not exceed 35% by volume. (Preferably it should
be below 30% and aromatic polycyclic aromatic
hydrocarbons (PAH*) content of the diesel fuel
should be below 10%.)
NOTICE: Mixing winter and summer fuel, using
Kerosene, residual fuel or Biocide produces poor
fuel quality and will result in reduced engine
performance and excessive wear of internal
components.