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VOLVO PENTA AQ125 AQ145 A B Workshop Service Repair Manual
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Workshop Manual
Engine Unit
AQ125A, B
AQ145A, B
C
2(0)


1
Safety Precautions ............................................................................................................. 2
General Information ........................................................................................................... 5
Repair Instructions ............................................................................................................ 6
Presentation ....................................................................................................................... 8
Repair Instructions
Disassembling, Overhauling and Inspection
Electrical parts, carburetor ................................................................................................... 9
Heating exchanger, exhaust pipe, oil filter .................................................................. 10–11
Oil cooler, sea water pump ............................................................................................... 12
Circulation pump, belt pulley, marking the timing belt ...................................................... 13
Belt tensioner, intermediate pulley, camshaft pulley ......................................................... 14
Sealing flange, flywheel cover .......................................................................................... 15
Vibration damper, intermediate shaft ................................................................................ 16
Camshaft ........................................................................................................................... 16
Cylinder head valves .................................................................................................. 16–18
Valve seats, guides, springs, pushers ........................................................................ 19–22
Flywheel, sealing .............................................................................................................. 22
Lubricating oil pump, pistons, crankshaft .................................................................... 23–24
Cylinders, pistons, connecting rods, crankshaft .......................................................... 25–28
Fuel pump, oil cooler, lubricating oil pump ................................................................. 28–30
Heat exchanger, carburetor, flywheel cover ................................................................ 31–33
Assembling
Crankshaft, pistons, lubrication oil pump, flywheel ..................................................... 33–35
Oil sump, cylinder head, camshaft .............................................................................. 36–37
Intermediate shaft, seals, camshaft gear wheel .......................................................... 38–39
Intermediate gear, marking, timing belt ....................................................................... 40–42
Oil pump drive, circulation pump, valve adjustment .................................................... 42–46
Distributor, oil cooler, exhaust pipe, heat exchanger .................................................. 46–48
Lubrication oil filter, sea water pump, expansion tank ................................................ 48–49
Thermostat sea water strainer, alternator .................................................................... 49–50
Starter motor, induction pipe, carburetor ..................................................................... 50–51
Electric wiring diagram ................................................................................................... 52
Fault finding chart ........................................................................................................... 53
Special tools .............................................................................................................. 54–55
Technical data AQ125A, AQ145A ............................................................................ 56–60
Valve adjusting kit ........................................................................................................... 61
Technical data AQ125B, AQ145B ............................................................................ 62–68
Contents

2
Safety Precautions
Check that the warning or information decals
on the product are always clearly visible. Re-
place decals that have been damaged or paint-
ed over.
Never use start spray or similar to start the
engine. The starter element may cause an ex-
plosion in the inlet manifold. Danger of person-
al injury.
Avoid opening the filler cap for engine coolant
system (freshwater cooled engines) when the
engine is still hot. Steam or hot coolant can
spray out. Open the coolant filler cap carefully
and slowly to release pressure before remov-
ing the cap completely. Take great care if a
cock, plug or engine coolant line must be re-
moved from a hot engine. It is difficult to anti-
cipate in which direction steam or hot coolant
can spray out.
Hot oil can cause burns. Avoid skin contact
with hot oil. Ensure that the lubrication system
is not under pressure before commencing
work on it. Never start or operate the engine
with the oil filler cap removed, otherwise oil
could be ejected.
Stop the engine and close the sea cock before
carrying out operations on the engine cooling
system.
Only start the engine in a well-ventilated area.
If operating the engine in an enclosed space,
ensure that exhaust gases and crankcase
ventilation emissions are ventilated out of the
working area.
Always use protective goggles where there is
a danger of pieces of metal, sparks from
grinding, acid or other chemicals being thrown
into your eyes. Your eyes are very sensitive,
injury can lead to loss of sight!
Introduction
This Workshop Manual contains technical data, de-
scriptions and repair instructions for Volvo Penta
products or product versions contained in the con-
tents list. Ensure that the correct workshop litera-
ture is being used.
Read the safety information and the Workshop
Manual “General Information” and “Repair In-
structions” carefully before starting work.
Important
In this book and on the engine you will find the fol-
lowing special warning symbols.
WARNING! If these instructions are not fol-
lowed there is a danger of personal injury, ex-
tensive damage to the product or serious me-
chanical malfunction.
IMPORTANT! Used to draw your attention to
something that can cause damage, product
malfunction or damage to property.
NOTE! Used to draw your attention to important infor
mation that will facilitate work or operations.
Below is a summary of the risks and safety precau-
tions you should always observe or carry out when
operating or servicing the engine.
Immobilize the engine by turning off the power
supply to the engine at the main switch
(switches) and lock it (them) in the OFF posi-
tion before starting work. Set up a warning no-
tice at the engine control point or helm.
Generally, all servicing should be carried out
with the engine switched off. Some work (car-
rying out certain adjustments for example) re-
quires the engine to be running. Approaching
a running engine is dangerous. Loose clothing
or long hair can fasten in rotating parts and
cause serious personal injury.
If working in proximity to a running engine,
careless movements or a dropped tool can re-
sult in personal injury. Avoid burns. Take pre-
cautions to avoid hot surfaces (exhausts, tur-
bochargers, charge air pipes and starter
elements etc.) and liquids in supply lines and
hoses when the engine is running or has been
turned off immediately prior to starting work
on it. Reinstall all protective parts removed
during service operations before starting the
engine.

3
Avoid skin contact with oil. Long-term or re-
peated contact with oil can remove the natural
oils from your skin. The result can be irrita-
tion, dry skin, eczema and other skin prob-
lems. Used oil is more dangerous to health
than new oil. Use protective gloves and avoid
using oil-soaked clothes and rags. Wash regu-
larly, especially before meals. Use the correct
barrier cream to prevent dry skin and to make
cleaning your skin easier.
Most chemicals used in products (engine and
transmission oils, glycol, petrol and diesel oil)
and workshop chemicals (solvents and paints)
are hazardous to health Read the instructions
on the product packaging carefully! Always
follow safety instructions (using breathing
apparatus, protective goggles and gloves for
example). Ensure that other personnel are not
unwittingly exposed to hazardous substances
(by breathing them in for example). Ensure
that ventilation is good. Handle used and ex-
cess chemicals according to instructions.
All fuels and many chemicals are inflammable.
Ensure that a naked flame or sparks cannot
ignite fuel or chemicals. Combined with air in
certain ratios, petrol, some solvents and hy-
drogen from batteries are easily inflammable
and explosive. Smoking is prohibited! Ensure
that ventilation is good and that the necessary
safety precautions have been taken before
carrying out welding or grinding work. Always
have a fire extinguisher to hand in the work-
place.
Store oil and fuel-soaked rags and fuel and oil
filters safely. In certain conditions oil-soaked
rags can spontaneously ignite. Used fuel and
oil filters are environmentally dangerous waste
and must be deposited at an approved site for
destruction together with used lubricating oil,
contaminated fuel, paint remnants, solvent,
degreasing agents and waste from washing
parts.
Never allow a naked flame or electric sparks
near the batteries. Never smoke in proximity
to the batteries. The batteries give off hydro-
gen gas during charging which when mixed
with air can form an explosive gas – oxyhy-
drogen. This gas is easily ignited and highly
volatile. Incorrect connection of the battery
can cause a spark which is sufficient to cause
an explosion with resulting damage. Do not
disturb battery connections when starting the
engine (spark risk) and do not lean over bat-
teries.
Never mix up the positive and negative bat-
tery terminals when installing. Incorrect instal-
lation can result in serious damage to electri-
cal equipment. Refer to wiring diagrams.
Always use protective goggles when charging
and handling batteries. The battery electrolyte
contains extremely corrosive sulfuric acid. If
this comes into contact with the skin, wash
immediately with soap and plenty of water. If
battery acid comes into contact with the eyes,
immediately flush with copious amounts of
water and obtain medical assistance.
Turn off the engine and turn off power at main
switch(es) before carrying out work on the
electrical system.
Use the lifting eyes mounted on the engine/re-
verse gear when lifting the drive unit.
Always check that lifting equipment is in good
condition and has sufficient load capacity to
lift the engine (engine weight including reverse
gear and any extra equipment installed).
To ensure safe handling and to avoid damag-
ing engine components on top of the engine,
use a lifting beam to raise the engine. All
chains and cables should run parallel to each
other and as perpendicular as possible in rela-
tion to the top of the engine.
If extra equipment is installed on the engine
altering its center of gravity, a special lifting
device is required to achieve the correct bal-
ance for safe handling.
Never carry out work on an engine suspended
on a hoist.

4
Never remove heavy components alone, even
where secure lifting equipment such as se-
cured blocks are being used. Even where lift-
ing equipment is being used it is best to carry
out the work with two people; one to operate
the lifting equipment and the other to ensure
that components are not trapped and damaged
when being lifted. When working on-board en-
sure that there is sufficient space to remove
components without danger of injury or dam-
age.
Components in the electrical system, ignition
system (gasoline engines) and fuel system on
Volvo Penta products are designed and con-
structed to minimize the risk of fire and explo-
sion. The engine must not be run in areas
where there are explosive materials.
Always use fuels recommended by Volvo Pen-
ta. Refer to the Instruction Book. The use of
lower quality fuels can damage the engine. On
a diesel engine poor quality fuel can cause the
control rod to seize and the engine to overrev
with the resulting risk of damage to the engine
and personal injury. Poor fuel quality can also
lead to higher maintenance costs.

5
General information
About the workshop manual
This workshop manual contains technical specifi-
cation, descriptions and instructions for repairing
the standard versions of the following engines
AQ125A, B – AQ145A, B. The workshop manual
displays the operations carried out on any of the
engines above. As a result the illustrations and pic-
tures in the manual that show certain parts on the
engines, do not in some cases apply to all the en-
gines listed above. However the repair and service
operations described are the same in all essential
details. Where they are not the same this is stated
in the manual and where the difference is consider-
able the operations are described separately. En-
gine designations and numbers are given on the
number plate. The engine designation and number
should be given in all correspondence about the en-
gine.
This Workshop Manual has been developed primari-
ly for Volvo Penta service workshops and qualified
personnel. Persons using this book are assumed to
have a grounding in marine drive systems and be
able to carry out related mechanical and electrical
work.
Volvo Penta is continuously developing their prod-
ucts. We therefore reserve the right to make chang-
es. All the information contained in this book is
based on product data available at the time of going
to print. Any essential changes or modifications in-
troduced into production or updated or revised ser-
vice methods introduced after the date of publica-
tion will be provided in the form of Service Bulletins.
Replacement parts
Replacement parts for electrical and fuel systems
are subject to statutory requirements (US Coast
Guard Safety Regulations for example). Volvo Pen-
ta Genuine parts meet these requirements. Any
type of damage which results from the use of non-
original Volvo Penta replacement parts for the prod-
uct will not be covered under any warranty provided
by Volvo Penta.

6
Repair instructions
The working methods described in the Service Man-
ual apply to work carried out in a workshop. The en-
gine has been removed from the boat and is in-
stalled in an engine fixture. Unless otherwise stated
reconditioning work which can be carried out with
the engine in place follows the same working
method.
Warning symbols occurring in the Workshop Man-
ual (for their meaning see Safety information)
WARNING!
IMPORTANT!
NOTE!
are not in any way comprehensive since it is
impossible to predict every circumstance under
which service work or repairs may be carried out.
For this reason we can only highlight the risks that
can arise when work is carried out incorrectly in a
well-equipped workshop using working methods and
tools developed by us.
All procedures for which there are Volvo Penta spe-
cial tools in this Workshop Manual are carried out
using these. Special tools are developed to rational-
ize working methods and make procedures as safe
as possible. It is therefore the responsibility of any
person using tools or working methods other than
the ones recommended by us to ensure that there is
no danger of injury, damage or malfunction resulting
from these.
In some cases there may be special safety precau-
tions and instructions for the use of tools and chem-
icals contained in this Workshop Manual. These
special instructions should always be followed if
there are no separate instructions in the Workshop
Manual.
Certain elementary precautions and common sense
can prevent most risks arising. A clean workplace
and engine eliminates much of the danger of injury
and malfunction.
It is of the greatest importance that no dirt or for-
eign particles get into the fuel system, lubrication
system, intake system, turbocharger, bearings and
seals when they are being worked on. The result
can be malfunction or a shorter operational life.
Our joint responsibility
Each engine consists of many connected systems
and components. If a component deviates from its
technical specification the environmental impact of
an otherwise good engine may be increased signi-
ficantly. It is therefore vital that wear tolerances are
maintained, that systems that can be adjusted are
adjusted properly and that Volvo Penta Genuine
Parts as used. The engine Maintenance Schedule
must be followed.
Some systems, such as the components in the fuel
system, require special expertise and special test-
ing equipment for service and maintenance. Some
components are sealed at the factory for environ-
mental reasons. No work should be carried out on
sealed components except by authorized personnel.
Bear in mind that most chemicals used on boats are
harmful to the environment if used incorrectly. Vol-
vo Penta recommends the use of biodegradable de-
greasing agents for cleaning engine components,
unless otherwise stated in a workshop manual.
Take special care when working on-board, that oil
and waste is taken for destruction and is not acci-
dentally pumped into the environment with bilge wa-
ter.
Tightening torques
Tightening torques for vital joints that must be
tightened with a torque wrench are listed in work-
shop manual “Technical Data”: “Tightening Torques”
and are contained in work descriptions in this Man-
ual. All torques apply for cleaned threads, screw
heads and mating surfaces. Torques apply for light-
ly oiled or dry threads. If lubricants, locking fluid or
sealing compound are required for a screwed joint
this information will be contained in the work de-
scription and in “Tightening Torques” Where no
tightening torque is stated for a joint use the general
tightening torques according to the tables below.
The tightening torques stated are a guide and the
joint does not have to be tightened using a torque
wrench.
Dimension Tightening Torques
Nm lbt.ft
M5 6 4.4
M6 10 7.4
M8 25 18.4
M10 50 36.9
M12 80 59.0
M14 140 103.3

7
Tightening torques-protractor (angle)
tightening
Tightening using both a torque set-
ting and a protractor angle requires
that first the recommended torque is
applied using a torque wrench and
then the recommended angle is add-
ed according to the protractor scale.
Example: a 90° protractor tightening
means that the joint is tightened a
further 1/4 turn in one operation af-
ter the stated tightening torque has
been applied.
Locknuts
Do not re-use lock nuts that have been removed
during dismantling as they have reduced service life
when re-used - use new nuts when assembling or
reinstalling. For lock nuts with a plastic insert such
as Nylock
®
the tightening torque stated in the table
is reduced if the Nylock
®
nut has the same head
height as a standard hexagonal nut without plastic
insert. Reduce the tightening torque by 25% for bolt
size 8 mm or larger. Where Nylock
®
nuts are high-
er, or of the same height as a standard hexagonal
nut, the tightening torques given in the table apply.
Tolerance classes
Screws and nuts are divided into different strength
classes, the class is indicated by the number on the
bolt head. A high number indicates stronger materi-
al, for example a bolt marked 10-9 indicates a high-
er tolerance than one marked 8-8. It is therefore im-
portant that bolts removed during the disassembly
of a bolted joint must be reinstalled in their original
position when assembling the joint. If a bolt must be
replaced check in the replacement parts catalogue
to make sure the correct bolt is used.
Sealants
A number of sealants and locking liquids are used
on the engines. The agents have varying properties
and are used for different types of jointing trengths,
operating temperature ranges, resistance to oil and
other chemicals and for the different materials and
gap sizes in the engines.
To ensure service work is correctly carried out it is
important that the correct sealant and locking fluid
type is used on the joint where the agents are re-
quired.
In this Volvo Penta Service Manual the user will find
that each section where these agents are applied in
production states which type was used on the en-
gine.
During service operations use the same agent or an
alternative from a different manufacturer.
Make sure that mating surfaces are dry and free
from oil, grease, paint and anti-corrosion agent be-
fore applying sealant or locking fluid. Always follow
the manufacturer’s instructions for use regarding;
temperature range, curing time and any other in-
structions for the product.
Two different basic types of agent are used on the
engine and these are:
RTV agent (Room temperature vulcanizing). Use for
gaskets, sealing gasket joints or coating gaskets.
RTV agent is clearly visible when a component has
been dismantled; old RTV must be removed before
the joint is resealed. Old sealant can be removed
using methylated spirits in all cases.
Anaerobic agents. These agents cure in an absence
of air. They are used when two solid parts, for ex-
ample cast components, are installed face-to-face
without a gasket. They are also commonly used to
secure plugs, threads in stud bolts, cocks, oil pres-
sure switches and so on. The cured material is
glass-like and it is therefore colored to make it vis-
ible. Cured anaerobic agents are extremely resist-
ant to solvents and the old agent cannot be re-
moved. When reinstalling the part is carefully
degreased and then new sealant is applied.

8
Presentation
1. Oil dipstick
2. Fresh water tank
3. Filler cap, checking, fresh water
4. Distributor
5. Carburettor, front (AQ125 has only one)
6. Intake air silencer
7. Carburettor, rear
8. Ignition coil
9. Electro-mechanical lift device
10. Steering arm
11. Fuse box (exec. USA)
12. Serial number
13. Fuse (exec. USA)
14. Fuse (not USA)
15. Fuel pump
16. Sea water pump
17. Grease joint, upper steering shaft journal
18. Grease joint, drive shaft journal
19. Oil filler cap engine
20. Water filter
21. Heat exchanger
22. Draining, sea water
23. Luboil filter
24. Oil cooler (only AQ145A)
25. Draining, sea water
26. Draining, sea water
27. Draining, fresh water
AQ145A AQ145A
AQ125
AQ125
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This workshop service repair manual for Volvo Penta AQ125 and AQ145 A/B engines contains over 70 pages of high-quality engine manual. It is a valuable resource for both professional mechanics and DIY enthusiasts.
- Safety Precautions - Page 2
- General Information - Page 5
- Repair Instructions - Page 6
- Presentation - Page 8
- Disassembling, Overhauling and Inspection
- Electrical parts, carburetor - Page 9
- Heating exchanger, exhaust pipe, oil filter - Pages 10-11
- Oil cooler, sea water pump - Page 12
- Circulation pump, belt pulley, marking the timing belt - Page 13
- Belt tensioner, intermediate pulley, camshaft pulley - Page 14
- Sealing flange, flywheel cover - Page 15
- Vibration damper, intermediate shaft - Page 16
- Camshaft - Page 16
- Cylinder head valves - Pages 16-18
- Valve seats, guides, springs, pushers - Pages 19-22
- Flywheel, sealing - Page 22
- Lubricating oil pump, pistons, crankshaft - Pages 23-24
- Cylinders, pistons, connecting rods, crankshaft - Pages 25-28
- Fuel pump, oil cooler, lubricating oil pump - Pages 28-30
- Heat exchanger, carburetor, flywheel cover - Pages 31-33
- Assembling
- Crankshaft, pistons, lubrication oil pump, flywheel - Pages 33-35
- Oil sump, cylinder head, camshaft - Pages 36-37
- Intermediate shaft, seals, camshaft gear wheel - Pages 38-39
- Intermediate gear, marking, timing belt - Pages 40-42
- Oil pump drive, circulation pump, valve adjustment - Pages 42-46
- Distributor, oil cooler, exhaust pipe, heat exchanger - Pages 46-48
- Lubrication oil filter, sea water pump, expansion tank - Pages 48-49
- Thermostat sea water strainer, alternator - Pages 49-50
- Starter motor, induction pipe, carburetor - Pages 50-51
- Electric wiring diagram - Page 52
- Fault finding chart - Page 53
- Special tools - Pages 54-55
- Technical data AQ125A, AQ145A - Pages 56-60
- Valve adjusting kit - Page 61
- Technical data AQ125B, AQ145B - Pages 62-68