Yanmar BY series User manual

BY series
4BY
6BY
SERVICE MANUAL

BY Service Manual
BY series
SERVICE MANUAL
4BY
6BY
P/N:0BBY0-G00100
MARINE
ENGINES

BY SERVICE MANUAL
ii BY Service Manual
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.
© 2006 Yanmar Marine International.
0406

4BY / 6BY Service Manual iii
4BY / 6BY Service Manual
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
Cooling System ................................................................................... 7-1
Lubrication........................................................................................... 8-1
Turbocharger....................................................................................... 9-1
Starter Motor...................................................................................... 10-1
Alternator ........................................................................................... 11-1
Electrical and ECU ............................................................................ 12-1
Troubleshooting................................................................................ 13-1

TABLE OF CONTENTS
iv 4BY / 6BY Service Manual
This Page Intentionally Left Blank

BY Service Manual 1-1
BY Service Manual Section 1
INTRODUCTION
This manual gives specific instructions for the proper repair of Yanmar BY series marine engines.
Please follow the procedures carefully to ensure quality service.
Yanmar recommends that you read this Service Manual completely before starting with repairs, as some of
the procedures described are rather complex.
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 an authorized Yanmar marine dealer or distributor for any questions you
have regarding this Service Manual.

INTRODUCTION
1-2 BY Service Manual
This Page Intentionally Left Blank

BY Service Manual 2-1
BY Service Manual Section 2
SAFETY
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 labels from becoming dirty or torn and
replace them if they are lost or damaged. Also, if
you need to replace a part that has a label attached
to it, make sure you order the new part and label at
the same time.
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.
ADANGER
Danger (the word “DANGER” is in white
letters with a red rectangle behind
it) - indicates an imminently hazardous
situation which, if not avoided, will
result in death or serious injury. Danger
is limited to the most extreme
situations.
0000001en
AWARNING
Warning (the word “WARNING” is in
black letters with an orange rectangle
behind it) – indicates a potentially
hazardous situation which, if not
avoided, could result in death or serious
injury.
0000001en
ACAUTION
Caution (the word “CAUTION” is in black
letters with a yellow rectangle behind it)
– indicates a potentially hazardous
situation which, if not avoided, may
result in minor or moderate injury.
0000001en
CAUTION
Caution without the safety alert symbol
indicates a potentially hazardous
situation that can cause damage to the
machine, personal property and / or the
environment or cause the machine to
operate improperly.
0000001en

SAFETY
2-2 BY Service Manual
Safety Precautions
SAFETY PRECAUTIONS
ADANGER
SCALD HAZARD!
• NEVER remove the coolant filler cap if
the engine is hot. Steam and hot
engine coolant will escape and
seriously burn you. Allow the engine
to cool before attempting to remove
the filler cap.
• Securely tighten the filler cap after
checking the coolant level. Steam can
escape during engine operation if the
cap is loose.
• Failure to comply will result in death or
serious injury.
0000002enMarine
ADANGER
EXPLOSION HAZARD!
• Keep the area around the battery
well-ventilated. While the engine is
running or the battery is charging,
hydrogen gas is produced which can
be easily ignited.
• Keep sparks, open flame and any other
form of ignition away while the engine
is running or battery is charging.
• Failure to comply will result in death or
serious injury.
0000003en
ADANGER
CRUSH HAZARD!
• ALWAYS use the engine lifting eyes
when lifting the marine engine. The
lifting eyes are engineered to lift the
weight of the marine engine only.
• ALWAYS use lifting equipment with
sufficient capacity to lift the marine
engine. Additional equipment is
necessary to lift the marine engine and
marine gear together.
• NEVER stand under hoisted marine
engine. If the hoist mechanism fails,
the marine engine will fall on you,
causing serious injury or death.
• Failure to comply will result in death or
serious injury.
0000026en
ADANGER
CRUSH HAZARD!
• NEVER stand under hoisted engine. If
the hoist mechanism fails, the engine
will fall on you, causing death or
serious injury.
• Failure to comply will result in death or
serious injury.
0000033enMarine

SAFETY
BY Service Manual 2-3
Safety Precautions
ADANGER
FIRE HAZARD!
• Keep fire extinguishers handy in case
of fire. Clearly indicate the location of
the fire extinguishers with a safety
sign.
• Ensure that the type of fire
extinguishers are appropriate for
material that might catch fire. Check
with local authorities.
• Have all fire extinguishers checked
periodically for proper operation
and / or readiness.
• Post evacuation routes prominently.
Periodically conduct fire drills.
• Ensure that appropriate fire detection
and extinguishing equipment are
installed and checked periodically for
proper operation. Check with local
authorities.
• Failure to comply will result in death or
serious injury.
0000018en
ADANGER
FIRE AND EXPLOSION HAZARD!
• Diesel fuel is flammable and explosive
under certain conditions.
• NEVER remove the fuel cap with the
engine running.
• Failure to comply will result in death or
serious injury.
0000011en
ADANGER
FIRE AND EXPLOSION HAZARD!
• Diesel fuel is flammable and explosive
under certain conditions.
• When you remove any fuel system
component to perform maintenance
(such as changing the fuel filter) place
an approved container under the
opening to catch the fuel.
• NEVER use a shop rag to catch the
fuel. Vapors from the rag are
flammable and explosive.
• Wipe up any spills immediately.
• Wear eye protection. The fuel system
is under pressure and fuel could spray
out when you remove any fuel system
component.
• Failure to comply will result in death or
serious injury.
0000009en
ADANGER
FIRE AND EXPLOSION HAZARD!
• Diesel fuel is flammable and explosive
under certain conditions.
• NEVER use diesel fuel as a cleaning
agent.
• Failure to comply will result in death or
serious injury.
0000012en

SAFETY
2-4 BY Service Manual
Safety Precautions
ADANGER
EXPLOSION HAZARD!
• NEVER check the remaining battery
charge by shorting out the terminals.
This will result in a spark and may
cause an explosion or fire. Use a
hydrometer to check the remaining
battery charge.
• If the electrolyte is frozen, slowly warm
the battery before you recharge it.
• Failure to comply will result in death or
serious injury.
0000007en
ADANGER
FIRE AND EXPLOSION HAZARD!
• Diesel fuel is flammable and explosive
under certain conditions.
• Before you operate the engine, check
for fuel leaks. Replace rubberized fuel
hoses every two years or every 500
hours of engine operation, whichever
comes first, even if the engine has
been out of service. Rubberized fuel
lines tend to dry out and become
brittle after two years or 500 hours of
engine operation, whichever comes
first.
• Failure to comply will result in death or
serious injury.
0000015enBY
ADANGER
NEVER start the engine unless the air
filter is installed.
Failure to comply will result in death or
serious injury.
0000025en
ADANGER
FIRE AND EXPLOSION HAZARD!
• Diesel fuel is flammable and explosive
under certain conditions.
• Only fill the fuel tank with diesel fuel.
Filling the fuel tank with gasoline may
result in a fire and will damage the
engine.
• NEVER refuel with the engine running.
• Wipe up all spills immediately.
• Keep sparks, open flames or any other
form of ignition (match, cigarette,
static electric source) well away when
refueling.
• NEVER overfill the fuel tank.
• Fill the fuel tank. Store any containers
containing fuel in a well-ventilated
area, away from any combustibles or
sources of ignition.
• Failure to comply will result in death or
serious injury.
0000005en

SAFETY
BY Service Manual 2-5
Safety Precautions
ADANGER
FIRE AND EXPLOSION HAZARD!
• Only use the key switch to start the
engine.
• NEVER jump-start the engine. Sparks
caused by shorting the battery to the
starter terminals may cause a fire or
explosion.
• Failure to comply will result in death or
serious injury.
0000004en
ADANGER
FIRE HAZARD!
Hot engine surfaces, such as the
exhaust pipe and turbocharger can
cause material such as oil and grease to
ignite.
• ALWAYS ensure the exhaust pipe,
turbocharger, and heat shields are
absolutely free of oil and grease.
Clean all grease and oil from the
exterior surfaces of the exhaust pipe
and turbocharger housing before
installing.
• ALWAYS install new gaskets and seals
for the turbocharger lubrication lines,
and check after installation for leaks.
• NEVER install a heat shield that is oily.
ALWAYS replace it with a new one.
• Failure to comply will result in death or
serious injury.
0000034en
ADANGER
CRUSH HAZARD!
• When you need to transport an engine
for repair, have a helper assist you to
attach it to a hoist and load it on a
truck.
• NEVER stand under a hoisted engine.
If the hoist mechanism fails, the
engine will fall on you, causing death
or serious injury.
• Failure to comply will result in death or
serious injury.
0000008en
AWARNING
ALCOHOL AND DRUG HAZARD!
• NEVER operate the engine while you
are under the influence of alcohol or
drugs.
• NEVER operate the engine when you
are feeling ill.
• Failure to comply could result in death
or serious injury.
0000004en

SAFETY
2-6 BY Service Manual
Safety Precautions
AWARNING
SEVER HAZARD!
• Keep hands and other body parts
away from moving / rotating parts
such as the flywheel or PTO shaft.
• Wear tight fitting clothing and keep
your hair short or tie it back while the
engine is running.
• Remove all jewelry before you operate
or service the engine.
• NEVER start the engine in gear.
Sudden movement of the engine
and / or vessel could cause death or
serious personal injury.
• NEVER operate the engine without the
guards in place.
• Before you start the engine make sure
that all bystanders are clear of the
area.
• Keep children and pets away while the
engine is operating.
• Check before starting the engine that
any tools or shop rags used during
maintenance have been removed from
the area.
• Failure to comply could result in death
or serious injury.
0000002enMarine
AWARNING
EXPOSURE HAZARD!
• Wear personal protective equipment
such as gloves, work shoes, eye and
hearing protection as required by the
task at hand.
• NEVER wear jewelry, unbuttoned
cuffs, ties or loose fitting clothing
when you are working near
moving / rotating parts such as the
flywheel or PTO shaft.
• ALWAYS tie back long hair when you
are working near moving / rotating
parts such as a flywheel or PTO shaft.
• NEVER operate the engine while
wearing a headset to listen to music or
radio because it will be difficult to hear
the warning signals.
• Failure to comply could result in death
or serious injury.
0000005enMarine
AWARNING
To prevent possible eye injury, always
wear SAFETY GLASSES while servicing
the engine.
0000013en

SAFETY
BY Service Manual 2-7
Safety Precautions
AWARNING
HIGH PRESSURE 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.
• Failure to comply could result in death
or serious injury.
0000008enMarine
AWARNING
SHOCK HAZARD!
• Turn off the battery switch (if
equipped) or disconnect the negative
battery cable before servicing the
electrical system.
• Check the electrical harnesses for
cracks, abrasions, and damaged or
corroded connectors. ALWAYS keep
the connectors and terminals clean.
• Failure to comply could result in death
or serious injury.
0000009en
AWARNING
ENTANGLEMENT HAZARD!
• Stop the engine before you begin to
service it.
• NEVER leave the key in the key switch
when you are servicing the engine.
Someone may accidentally start the
engine and not realize you are
servicing it. This could result in a
serious injury.
• If you must service the engine while it
is operating, remove all jewelry, tie
back long hair, and keep your hands,
other body parts and clothing away
from moving / rotating parts.
• Failure to comply could result in death
or serious injury.
0000010en
AWARNING
BURN HAZARD!
• If you must drain the engine oil while it
is still hot, stay clear of the hot engine
oil to avoid being burned.
• ALWAYS wear eye protection.
• Failure to comply could result in death
or serious injury.
0000011en

SAFETY
2-8 BY Service Manual
Safety Precautions
AWARNING
BURN HAZARD!
• Wait until the engine cools before you
drain the engine coolant. Hot engine
coolant may splash and burn you.
• Failure to comply could result in death
or serious injury.
0000016en
AWARNING
SUDDEN MOVEMENT HAZARD!
• Shift the marine gear into the
NEUTRAL position any time the
engine is at idle.
• Failure to comply could result in death
or serious injury.
0000023en
AWARNING
BURN HAZARD!
• Keep your hands and other body parts
away from hot engine surfaces such
as the muffler, exhaust pipe,
turbocharger and engine block during
operation and shortly after you shut
the engine down. These surfaces are
extremely hot while the engine is
operating and could seriously burn
you.
• Failure to comply could result in death
or serious injury.
0000015enBY
AWARNING
FUME / BURN HAZARD!
• Always read and follow safety related
precautions found on containers of
hazardous substances like parts
cleaners, primers, sealants and
sealant removers.
• Failure to comply could result in death
or serious injury.
0000014en
AWARNING
SUDDEN MOVEMENT HAZARD!
• Be sure the boat is in open water away
from other boats, docks, and other
obstructions before increasing rpm.
• Failure to comply could result in death
or serious injury.
0000006enMarine
AWARNING
BURN HAZARD!
• Handle hot components with
heat-resistant gloves.
• Failure to comply could result in death
or serious injury.
0000110en

SAFETY
BY Service Manual 2-9
Safety Precautions
AWARNING
EXHAUST HAZARD!
• NEVER operate the engine in an
enclosed area such as a garage,
tunnel, underground room, manhole or
ship’s hold without proper ventilation.
• NEVER block windows, vents, or other
means of ventilation if the engine is
operating in an enclosed area. All
internal combustion engines create
carbon monoxide gas during
operation. Accumulation of this gas
within an enclosure could cause
illness or even death.
• Make sure that all connections are
tightened to specifications after repair
is made to the exhaust system.
• Failure to comply could result in death
or serious injury.
0000003en
AWARNING
BURN HAZARD!
• Batteries contain sulfuric acid. NEVER
allow battery fluid to come in contact
with clothing, skin or eyes. Severe
burns could result. ALWAYS wear
safety goggles and protective clothing
when servicing the battery. If battery
fluid contacts the eyes and / or skin,
immediately flush the affected area
with a large amount of clean water and
obtain prompt medical treatment.
• Failure to comply could result in death
or serious injury.
0000007en
ACAUTION
COOLANT HAZARD!
• Wear eye protection and rubber gloves
when you handle Long Life engine
coolant. If contact with the eyes or
skin should occur, flush eyes and
wash immediately with clean water.
• Failure to comply may result in minor
or moderate injury.
0000005enMarine

SAFETY
2-10 BY Service Manual
Safety Precautions
ACAUTION
FLYING OBJECT HAZARD!
• ALWAYS wear eye protection when
servicing the engine and when using
compressed air or high-pressure
water. Dust, flying debris, compressed
air, pressurized water or steam may
injure your eyes.
• Failure to comply may result in minor
or moderate injury.
0000003en
ACAUTION
POOR LIGHTING HAZARD!
• Ensure that the work area is
adequately illuminated.
• Use task lighting to illuminate areas
that need additional illumination.
• Always place wire cage on portable
safety lamps.
• Failure to comply may result in minor
or moderate injury.
0000023en
ACAUTION
TOOL HAZARD!
• Use tools appropriate for the task at
hand.
• Use the correct size tool for loosening
or tightening machine parts.
• Failure to comply may result in minor
or moderate injury.
0000024en
ACAUTION
Be sure to secure the engine solidly to
prevent injury or damage to parts due to
the engine falling during work on the
engine.
0000009en
ACAUTION
RISK OF CRUSH INJURY
The starter motor is very heavy. Use
care when removing the starter motor.
0000032en
ACAUTION
PINCH HAZARD!
Use care not to catch finger between
belt and pulley while installing belt.
Failure to comply may result in minor or
moderate injury.
0000034en
CAUTION
If any problem is noted during the visual
check, the necessary corrective action
should be taken before you operate the
engine.
0000021en
CAUTION
• NEVER overfill the engine with engine
oil.
• ALWAYS keep the oil level between the
upper and lower lines on the dipstick.
0000015enBY

SAFETY
BY Service Manual 2-11
Safety Precautions
CAUTION
• Only use the engine oil specified.
Other engine oils may affect warranty
coverage, cause internal engine
components to seize and / or shorten
engine life.
• Prevent dirt and debris from
contaminating the engine oil. Carefully
clean the dipstick and the surrounding
area before you remove the cap.
• NEVER mix different types of engine
oil. This may adversely affect the
lubricating properties of the engine oil.
• NEVER overfill. Overfilling may result
in white exhaust smoke, engine
overspeed or internal damage.
0000005enBY
CAUTION
• Only use the engine coolant specified.
Other engine coolants may affect
warranty coverage, cause an internal
buildup of rust and scale and / or
shorten engine life.
• Prevent dirt and debris from
contaminating engine coolant.
Carefully clean the filler cap and the
surrounding area before you remove
the cap.
• NEVER mix different types of engine
coolants. This may adversely affect the
properties of the engine coolant.
0000006enMarine
CAUTION
NEVER engage the starter motor while
the engine is running. This may damage
the starter motor pinion and / or ring
gear.
0000012en
CAUTION
Keep the piston pin parts, piston
assemblies, and connecting rod
assemblies together to be returned to
the same position during the
reassembly process. Label the parts
using an appropriate method.
0000088en
CAUTION
DO NOT remove special tools until
high-pressure pump is installed. If the
special tools are removed, the drive
sprocket will no longer be held in the
correct position for reassembly.
0000200en
CAUTION
• ALWAYS be environmentally
responsible.
• 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 irresponsibly by dumping
them into a sewer, on the ground, or
into ground water or waterways.
• Failure to follow these procedures may
seriously harm the environment.
0000013en

SAFETY
2-12 BY Service Manual
Safety Precautions
CAUTION
Protect the air cleaner, turbocharger (if
equipped) and electric components
from damage when you use steam or
high-pressure water to clean the engine.
0000014en
CAUTION
If the oil pump must be replaced, replace
it as an assembly only. Do not replace
individual components.
0000030en
CAUTION
Do not remove the positive (+) battery
cable from alternator terminal B while
the engine is operating. Damage to the
alternator will result.
0000037en
CAUTION
Do not turn the battery switch OFF while
the engine is operating. Damage to the
alternator will result.
0000038en
CAUTION
Do not operate the engine if the
alternator is producing unusual sounds.
Damage to the alternator will result.
0000039en
CAUTION
Do not use a high-pressure wash
directly on the alternator. Water will
damage the alternator and result in
inadequate charging.
0000049en
CAUTION
Do not reverse the positive (+) and
negative (-) ends of the battery cable.
The alternator diode and stator coil will
be damaged.
0000050en
CAUTION
Identify all parts and their location using
an appropriate method. It is important
that all parts are returned to the same
position during the reassembly process.
0000080en
CAUTION
Never use a steel wire brush to clean
fuel injectors. Damage to the nozzle and
other components is likely to result.
0000172en
CAUTION
Ensure that no fuel enters the cylinder
from the disconnected fuel system
components.
If fuel runs into the combustion
chamber, it must be removed
immediately using a pump.
Failure to do so could cause hydraulic
lock resulting in engine damage.
0000182en
CAUTION
NEVER hold the key in the START
position for longer than 10 seconds or
the starter motor will overheat.
0000201en

SAFETY
BY Service Manual 2-13
Safety Precautions
CAUTION
NEVER operate the engine with the
batteries disconnected. Damage to the
alternator will result.
0000185en
CAUTION
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.
0000119en
CAUTION
Immediately cap or plug all openings to
prevent contamination of system.
0000199en
CAUTION
NEVER use an engine starting aid such
as ether. Engine damage will result.
0000009en