Yanmar 6LT Series User manual

6LT Series Operation Manual i
TABLE OF
CONTENTS
6LT Series Operation Manual
Page
Introduction ............................................................................................. 1
Record of Ownership........................................................................... 2
Safety........................................................................................................ 3
Safety Precautions .............................................................................. 4
Product Overview.................................................................................... 9
Yanmar 6LT Common Rail Series Features and Applications ............ 9
New Engine Break-in........................................................................... 9
Component Identification................................................................... 10
Nameplates ....................................................................................... 14
Vessel Control System (VC20).......................................................... 16
Control the Backup Panel.................................................................. 22
Engine Management from Relay Box................................................ 23
Before You Operate............................................................................... 25
Diesel Fuel Specifications ................................................................. 26
Refilling.............................................................................................. 28
Engine Operation .................................................................................. 29
Preliminary Checks ........................................................................... 30
For Proper Use of the Engine............................................................ 30

TABLE OF CONTENTS
ii 6LT Series Operation Manual
Special Warnings .............................................................................. 30
VC20 Starting the Engine.................................................................. 32
Warm Up Mode (Shift Disconnect).................................................... 33
Throttle and Shift Control .................................................................. 34
Engine Speed Limit Mode ................................................................. 34
Cautions During Operation................................................................ 35
Shutting down the Engine (Stopping)................................................ 36
Checking the Engine After Operation................................................ 37
Inspection and Maintenance ................................................................ 39
Safety Precautions ............................................................................ 39
Precautions ....................................................................................... 40
EPA Maintenance Requirements ...................................................... 42
Maintenance Schedule...................................................................... 43
Maintenance Procedures .................................................................. 45
Check the Engine Oil Level............................................................... 45
Check the Oil Level in the Marine Gear ............................................ 45
Check the Coolant Level ................................................................... 46
Check the Condition of the Exhaust Duct(s) ..................................... 46
Draining the Water From the Fuel Pre-filter ...................................... 47
Check the Electrolyte Level of the Batteries – Clean Terminals ....... 48
Clean the Air Filter ............................................................................ 49
Check the State of Corrosion of the Zinc Anodes ............................. 50
Change the Engine Oil ...................................................................... 51
Change Engine Oil Filters ................................................................. 52
Change the Fuel Filter....................................................................... 53
Change Fuel Pre-filter ....................................................................... 54
Check Tension and Condition of Auxiliary Belt ................................. 55
Change Engine Coolant .................................................................... 56
Change Air Filter ............................................................................... 57
Change Oil Vapor Filters................................................................... 57
Periodic and Extraordinary Maintenance Operations........................ 58
Change the Auxiliary Belt.................................................................. 59

TABLE OF CONTENTS
6LT Series Operation Manual iii
Long Term Storage ............................................................................... 61
Preparing the Engine for Long Term Storage ................................... 61
Engine Start-up after a Long Period of Inactivity............................... 62
Directions for the First Start-up and Start-up after a Long Period of
Inactivity ............................................................................................ 62
Engine Malfunctions ............................................................................. 63
Specifications........................................................................................ 65
EPA Warranty USA Only....................................................................... 67
EU Declaration of Conformity .............................................................. 70

TABLE OF CONTENTS
iv 6LT Series Operation Manual
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6LT Series Operation Manual 1
6LT Series Operation Manual
INTRODUCTION
Welcome to the world of Yanmar Marine!
Yanmar Marine offers engines, drive systems and
accessories for all types of boats, from runabouts to
sailboats, and from cruisers to mega yachts. In
marine leisure boating, the worldwide reputation of
Yanmar Marine is second to none. We design our
engines to respect nature. This means quieter
engines, with minimal vibrations, cleaner than ever.
All of our engines meet applicable regulations,
including emissions, at the time of manufacture.
To help you enjoy your Yanmar 6LT series engine
for many years to come, please follow these
recommendations:
• Read and understand this Operation Manual
before you operate the machine to ensure that
you follow safe operating practices and
maintenance procedures.
• Keep this Operation Manual in a convenient
place for easy access.
• If this Operation Manual is lost or damaged, order
a new one from your authorized Yanmar Marine
dealer or distributor.
• Make sure this manual is transferred to
subsequent owners. This manual should be
considered a permanent part of the engine and
remain with it.
• Constant efforts are made to improve the quality
and performance of Yanmar products, so some
details included in this Operation Manual may
differ slightly from your engine. If you have any
questions about these differences, please consult
your authorized Yanmar Marine dealer or
distributor.
• The specifications and components (instrument
panel, fuel tank, etc.) described in this manual
may differ from ones installed on your vessel.
Please refer to the manual provided by the
manufacturer of these components.
• Refer to the Yanmar Limited Warranty Handbook
for a complete warranty description.

INTRODUCTION
26LT Series Operation Manual
RECORD OF OWNERSHIP
Take a few moments to record the information you need when you consult Yanmar for service, parts or
documentation.
Engine Model: ______________________________________________________________________
Engine Serial No.: ___________________________________________________________________
Date Purchased: ____________________________________________________________________
Dealer: ____________________________________________________________________________
Dealer Phone: ______________________________________________________________________
QTo Register Your Yanmar Engine
1. Visit https://yanmar.microsoftcrmportals.com/
or our website: https://www.yanmar.com/marine/
2. Click on “Register Your Engine”.

6LT Series Operation Manual 3
6LT Series Operation Manual
SAFETY
Yanmar considers safety of great importance and
recommends that anyone that comes into close
contact with its products, such as those who install,
operate, maintain or service Yanmar products,
exercise care, common sense and comply with the
safety information in this manual and on the
machine’s safety decals. 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.
DANGER
Indicates a hazardous situation which, if not
avoided, will result in death or serious injury.
WARNING
Indicates a hazardous situation which, if not
avoided, could result in death or serious injury.
CAUTION
Indicates a hazardous situation which, if not
avoided, could result in minor or moderate
injury.
NOTICE
Indicates a situation which can cause damage to
the machine, personal property and/or the
environment, or cause the equipment to operate
improperly.
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
46LT Series Operation Manual
SAFETY PRECAUTIONS
General Information
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 operation or
performing repairs or maintenance.
Before You Operate
DANGER
The safety messages that follow have DANGER
level hazards.
Never permit anyone to install or
operate the engine without proper
training.
Read and understand this Operation Manual
before you operate or service the engine to
ensure that you follow safe operating practices
and maintenance procedures.
Safety signs and labels are additional
reminders for safe operating and maintenance
techniques.
Consult authorized Yanmar Marine dealer or
distributor for additional training.
During Operation and Maintenance
WARNING
The safety messages that follow have
WARNING level hazards.
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 flames and any other
form of ignition out of the area.
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.
Fire Hazard
Undersized wiring systems can
cause an electrical fire.
Never use improper capacity of
fuses.
Store any containers containing fuel or other
flammable products in a well-ventilated area,
away from any combustibles or source of
ignition.
Store any equipment in a designated area away
from moving parts.
Never use the engine compartment for storage.

SAFETY
6LT Series Operation Manual 5
WARNING
Sever Hazard
Rotating parts can cause severe
injury or death. 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.
Alcohol and Drug Hazard
Never operate the engine while under
the influence of alcohol or drugs, or
when feeling ill.
Exposure Hazard
Always wear personal protective
equipment including appropriate
clothing, gloves, work shoes, and
eye and hearing protection as
required by the task at hand.
Sudden Movement Hazard
Never operate the engine while wearing a
headset to listen to music or radio because it
will be difficult to hear the warning signals.
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.
Exhaust Hazard
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 and
special precautions are required to avoid
carbon monoxide poisoning.
CAUTION
The safety messages that follow have CAUTION
level hazards.
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.
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 you handle engine
coolant. If contact with the eyes or
skin should occur, flush eyes and wash
immediately with clean water.

SAFETY
66LT Series Operation Manual
NOTICE
The safety messages that follow have NOTICE
level hazards.
It is important to perform daily checks as listed in
the Operation Manual. Periodic maintenance
prevents unexpected downtime, reduces the
number of accidents due to poor engine
performance and helps extend the life of the
engine.
Consult authorized Yanmar Marine dealer or
distributor if you need to operate the engine at high
altitudes. At high altitudes the engine will lose
power, run rough and produce exhaust gases that
exceed the design specifications.
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 by dumping
them into a sewer, on the ground, or into ground
water or waterways.
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.
NOTICE
If you have an installation with two or three engines
and only one engine is operating, the water pickup
(thru-hull) of the non-running engine(s) should be
closed. This will prevent water from being forced
past the seawater pump and eventually finding its
way into the engine. The result of water entering
the engine could cause seizure or other serious
problems.
If you have an installation with two or three
engines, and only one engine is operating, please
note that if the propeller shaft thru-hull (stuffing box)
is lubricated by engine water pressure and the
engines are interconnected, care must be taken
that water from the running engine does not enter
the exhaust of the non-running engine(s). This
water could cause seizure of the non-running
engine(s). Consult authorized Yanmar Marine
dealer or distributor for a complete explanation of
this condition.
If you have an installation with two or three
engines, and only one engine is operating, it is
important to limit the amount of throttle applied to
the running engine. If you observe black smoke or
movement of the throttle does not increase engine
speed, you are overloading the engine that is
running. Immediately throttle back to approximately
2/3 throttle or to a setting where the engine
performs normally. Failure to do so may cause the
running engine to overheat or cause excess carbon
buildup which may shorten the engine’s life.
Never turn off the battery switch (if equipped) or
short the battery cables during operation. Damage
to the electrical system will result.

SAFETY
6LT Series Operation Manual 7
Safety Signs
Some warning labels shown below are affixed to the engine.
NOTE: Labels containing an exclamation mark highlight a
potential danger.
Lifting point (only the engine). Risk of burns:
Expulsion of pressurised hot water.
Fuel filling cap
(on the tank, if present).
Risk of burns:
Presence of parts at high temperature.
Engine oil filling cap. Risk of fire:
Presence of fuel.
Engine oil level dipstick. Risk of injury from moving parts:
Presence of fans, pulleys, belts or other.

SAFETY
86LT Series Operation Manual
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6LT Series Operation Manual 9
6LT Series Operation Manual
PRODUCT
OVERVIEW
YANMAR 6LT COMMON RAIL
SERIES FEATURES AND
APPLICATIONS
The 6LT common rail series are four-stroke diesel
engines equipped with direct injection common rail
system and with liquid coolant systems.
The 6LT is 6-cylinder and turbocharged with an air
to seawater intercooler.
The engines are typically equipped with a marine
gear. (Optional)
These engines are designed for recreational and
light duty commercial craft use.
Applying for any other purpose except recreational
and light duty commercial can lead to reduced
vessel performance, lead to increased smoke
levels and cause permanent damage to your
engine.
The engine must be installed correctly with coolant
lines, exhaust gas lines and electrical wiring. No
auxiliary equipment without prior agreement by YMI
is allowed. To handle the drive equipment,
propulsion systems (including the propeller) and
other inboard equipment, always observe the
instructions and cautions given in the operation
manuals supplied by the boatyard and equipment
manufacturers.
The 6LT common rail series engines are designed
to be operated at maximum throttle (*1) for less
than 5% of total engine time (30 minutes out of
every 10 hours) and at maximum cruising speed or
less the rest of the time (*2).
The laws of some countries may require hull and
engine inspections, depending on the use, size and
cruising area of the boat. The installation, fitting and
surveying of this engine all require specialized
knowledge and engineering skills. See Yanmar’s
local subsidiary in your region or your authorized
Yanmar Marine dealer or distributor.
*1 maximum throttle: fuel stop power engine
speed, 2530 RPM.
*2 cruising speed: 90% load, 2400 RPM.
NEW ENGINE BREAK-IN
Thanks to modern engine construction
technologies a particular run-in procedure is not
required. However, it is recommended to avoid
using the engine at high or low power for long
periods during the first 50 hours.

PRODUCT OVERVIEW
10 6LT Series Operation Manual
COMPONENT IDENTIFICATION
Right side view
1 Air filter
2 Fuel filter
3 High-pressure pump for common rail
system
4 Seawater pump inlet
5 Air-seawater heat exchanger
6 Sacrificial anodes
7 Lifting eye
8 Coolant Filler Cap
9 Engine coolant-seawater heat exchanger
10 Starter motor
11 Seawater Drain
Figure 1

PRODUCT OVERVIEW
6LT Series Operation Manual 11
Left side view
1 Oil filters
2 Coolant expansion tank
3 Oil level dipstick
4 Oil filler cap
5 Lifting eye
6 Electronic control unit
7 Exhaust and seawater outlet
8 Turbocharger
9 Oil sump
10 Oil drain plug
11 Oil sump evacuation pump
Figure 2

PRODUCT OVERVIEW
12 6LT Series Operation Manual
Front view
1 Coolant expansion tank
2 Oil filter
3 Thermostat body
4 Coolant inlet pipe going to engine water
pump
5 Oil evacuation pump
6 Engine mounts
7 Pulley on crankshaft
8 Oil sump
9 Seawater pump inlet
10 Engine coolant-seawater heat exchanger
11 Blow-by gas valve
12 Oil filler cap
Figure 3

PRODUCT OVERVIEW
6LT Series Operation Manual 13
Rear view
1 Air filter
2 Fuel Pipes
3 Seawater pump inlet
4 Engine mounts
5 Engine flywheel
6 Oil sump
7 Turbine geometry actuator
8 Coolant expansion tank
9 Turbocharger
10 Oil filler cap
11 Intake pipe
Figure 4

PRODUCT OVERVIEW
14 6LT Series Operation Manual
NAMEPLATES
IDENTIFICATION DATA
The plates are fixed to the engine coolant tank.
Figure 5
6LT500
6LT580
6LT640
ENGINE NAMEPLATE LABEL
ON EXPANSION TANK

PRODUCT OVERVIEW
6LT Series Operation Manual 15
Figure 6
6LT500
6LT580
6LT640
EPA LABEL ON
EXPANSION TANK

PRODUCT OVERVIEW
16 6LT Series Operation Manual
VESSEL CONTROL SYSTEM (VC20)
The 6LT series engine is a fully electronically controlled engine, using Yanmar’s original “Vessel Control
System (VC20)”.
The control equipment consists of the Switch Panel, the Display, the Drive & Helm ECU, the Control Head
and the Backup Panel, which are connected by the cable harness to the engine and marine gear or stern
drive for remote control operation.
NOTE: The Yanmar Vessel Control System (VC20) was designed to operate the 6LT engine and drive
system. There are many control functions and diagnostic functions that are integrated together to insure
safe operation. If this system is not utilized in specific accordance with the instructions in this manual or the
system is modified in any way, Yanmar will not be responsible for any warranty failures in the operation of
the system or the vessel utilizing the system. Yanmar has designed the Vessel Control System (VC20) in
conjunction with the 6LT engine. The system has many functions that must be configured and calibrations
must be made before the vessel can be operated. Please arrange to have a Yanmar trained technician
inspect the vessel prior to the vessels operation.
Figure 7
To engine
Marine gear or
Shift Actuator
To engine
1
Marine gear or
Shift Actuator
To engine
To engine
No. Description
1 Shift and Throttle Control Head
2 Emergency Stop Switch (Option)
3 Switch Panel (to start and stop the engine)
4 Display
5HelmECU
6DriveECU
7 Backup Panel
8 Cable Harness Set
9 Adapter, Terminal