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The Thornycroft 90 and 108 engines are both 4 cylinder, 4 stroke naturally
aspirated high speed diesel units, both engines having electrically operated heater
plugs to aid cold starting.
The cast iro n crankcase with ri bbed sidewalls houses a forged steel, fully
counterbalanced crankshaft carried in three or five bearings respectively.
A full press ure wet sump lubric ation system is emplo yed with a full flow
detachable element type oil filter and integrated lubricating oil cooler.
The cooling system is indirect and usually employs an engine mounted heat
exchang er with a belt dr iven ra w wa ter pu mp. This sy stem is known as I FWC
(internal fresh water cooled).
An optional system is EFWC (external fresh water cooled.) This system utilizes the
engine fresh water pump and usually employs skin tanks attached to the hull to serve as heat
The single belt driven alternator and fresh water pump drive include a manual
belt tensioning arrangement for low maintenance completes the comprehensive
4 Cylinder naturally aspirated
4 Cylinder naturally aspirated
Power intermittent at 3500rpm = 36BHP Power intermittent at 3500rpm = 47BHP
continuous at 3000rpm = 30BHP continuous at 3000rpm = 38BHP
Maximum torque at 2500rpm = 531bf ft Maximum torque at 2400rpm = 731bf ft
Idle speed = 570rpm Idle speed = 570rpm
Minimum full load speed = 1500rpm Minimum full load speed = 1500rpm
The type 90 Engine may be set to develop continuous outputs from 13.5 to 30 BHP according to
The type 108 Engine may be set to develop continuous outputs from 21 to 38 BHP
according to requirements.
For special applications where full power will not be required for periods in
excess of 1 hour in any 12 hours consecutive running the engine can be supplied at an
intermittent rating as shown above.
NOTE: All horsepower ratings quoted are at the engine flywheel. Due allowance must
be made for transmission losses which will depend on the type of gearbox fitted.
For tropical use it is necessary to derate the engine by 2% for each 5%°C (10°F)
above 30°C (85°F) air temperature at sea level. In some parts of the wor ld
fur the r de rat ing for h umi dity is n ece ssar y in acco rda nce with
INITIAL STARTING OF ENGINE
_. Engine mounting and dipstick marking. Filling engine with oil.
2. Lubricant specification for engine and gearbox. Filling gearbox.
3. Coolant/Corrosion inhibitor specification. Filling cooling system.
4. Priming the engine oil system.
5. Bleeding the fuel system type 90 engines.
6. Bleeding the fuel system type 108 engines.
7. Initial start. Normal start. Running in.
8. Operating guidelines.
9. Operating guidelines.
Engine oil and filter change
10. Engine oil and filter change
11. Fuel filter change. Cleaning Type 90 engines.
12. fuel lift pump. Gearbox oil Type 108 engines.
13. change. Cleaning air filter.
14. Alternator drive belt adjustment
15. and replacement. Raw water pump
16. adjustment and replacement.
17. Checking and setting valve
clearances. Procedure for
retorquing cylinder head nuts. Removal/Refitting
18. fuel injectors.
19 Changing coolant.
20. Draining raw water system.
21. External fresh water cooled engines.
22. Electrical system.
23. Fault finding.
24. Fault finding.
25. Laying up the engine.
CHECKING ENGINE MOUNTING,
THORNYCROFT MARKING DIPSTICK, FILLING ENGINE WITH OIL
CHECKING ENGINE MOUNTING
The maximum installed angle of the engine is 15°, engine types 90/2, 108 and 108/2
(10° for engine type 90). This allows for a further rise of 4° when the craft is
moving. Check the angle of installation using the centreline of the mounting feet
bolts as a datum. Measure vertically on the centreline of the underside of the
front mounting foot bolt to find the angle of installation Fig. 1
Type 90 Type 90/2 Type 108
A 93mm = 10° A 138mm = 150 A 136mm = 15°
46mm = 5° 93mm = 10° 91mm = 10°
46mm = 5° 46mm = 5°
MARKING DIPSTICK, FILLING WITH OIL
Your engine is despatched from the factory without engine or gearbox oil and with an
unmarked engine dipstick. After the boat is launched, and is resting at
its normal trim angle, remove the oil filler cap from the rocker box Fig. 2 and pour 3.9
litres for type 90, 4.5 litres for type 90/2 or 4.8
litres for type 108 of specified lubricant through the filler
hole. Allow 5 minutes for .the oil to drain into the sump,
withdraw the dipstick and mark it for maximum oil level Fig.
3 (Use a centre punch for marking as filing a notch can
cause fatigue and eventual breakage while the engine is
running). Then mark dipstick using the same method 12.7mm
(%") below the maximum mark and this will be the minimum
LUBRICANT ENGINE AND GEARBOX
FT `Page 2
RUNNING IN OILS
Do NOT use special running-in lubricating oils for new or rebuilt engines. Use the
lubricating oils specified for normal engine operation.
ENGINE OIL VISCOSITY RECOMMENDATIONS
The use of a multi- graded lubric ating oil h as been fou nd to impro ve oil
consumption and improve engine cranking in cold temperatures while maintaining
lubrication at high operating temperatures. A multi-grade oil conforming to
MIL-L-20104B is. recommended with the viscosity grades shown in Fig. 4. The use of
single grade lubricating oil is not recommended except for synthetic oils used
in arctic conditions.
Atmospheric Temperature Viscosity
Above -10°C 20W50
-20°C to 10°C 1OW30 or 1OW40
Below -10°C 5W30 or 5W40
Borg Warner Automatic Transmission Fluid (T ype A)
Hurth Automatic Trnamsission Fluid (T ype A)
Newage PRM SAE 20 Engine Oil Minus 18°C to 0°C
SAE 30 engine Oil Above 0°C
FILLING THE GEARBOX
Remove the oil filler plug combined dipstick from the top of the gearbox. This is
in approximately the same position on Hurth, Newage PRM and Borg Warner. Using
a plastic bottle or funnel, fill the gearbox up to the maximum mark on the
dipstick. There is one level mark on the Hurth dipstick, the others have high
and low marks.
THORNYCROFT COOLING SYSTEM
Use anti-freeze during all seasons to protect the engine cooling system from
corrosion as well as freeze damage. Using the following anti-freeze solution %.
25% 3 3% 5 0%
Solution Solution Solution
Complete protection lO°F(-12C) 3°F(-16C) - 4°F(-20°C)
Safe protection 1°F(-17C) -8°F(-22C) -18°F(-28°C)
In tropical climates where anti-freeze availability may be limited, corrosion
inhibitor to protect the engine cooling system. use a
NOTE: Corrosion inhibitor is NOT an anti-freeze. COOLANT QUANTITIES
Complete system including engine (IFWC) types 90 and 108 engines.
For external fresh water cooled engines (EFWC) See Page 23. FILLING THE COOLING
Remove the filler cap from the heat exchanger Fig. 6 and fill the system
with coolant. This will take approximately 5 minutes as the system self
bleeds. Fill to 5mm below the filler neck level mark. Refit filler cap.
M Fig. 8
M Fig. 9
PRIMING THE ENGINE OIL SYSTEM THOMYCWFT
PRIMING THE ENGINE OIL SYSTEM (TYPE 90/2R ENGINES ONLY)
As only a residual amount of oil is present in the oil pump, filter and oil
galleries of the engine, it is therefore necessary to prime the system before the
engine is run. Connect the engine starter batteries disconnect power to the
fuel solenoid valve on the injection pump Fig. 7 and crank the engine over using
the key starter switch until pressure registers on the oil pressure gauge.
Stop cranking and check the engine and gearbox for oil or water leaks. Replace
PRIMING THE ENGINE OIL SYSTEM (TYPE 90 AND/108 ENGINES)
As only a residual amount of oil is present in the oil pump filter and oil
galleries of the engine it is therefore necessary to prime the system before the
engine is run. Connect the engine starter batteries, operate the key starter
switch with the stop control out, crank the engine over until pressure registers
on the oil pressure gauge. Stop cranking and check the engine and gearbox for
oil or water leaks.
THORNYCROFT BLEEDING THE FUEL SYSTEM TYPE 90 ENGINES
BLEEDING THE FUEL SYSTEM
Slacken the bleed valve on the injection pump Fig. 8. Operate the lift pump
Fig. 9 and when the fuel coming from the valve is free of air bubbles, tighten the
Slacken the uni ons at the
injector ends of a ny two high p ressure pipes. Fig. 10. Ensure that the stop
control is in the run position and the engine speed control is in the fully
open position. Crank the engine until the fuel coming from both pipes is free from air
bubbles, then tighten the unions.
NB. After initial start procedure has been observed start the engine and allow it
to idle until it is running evenly on all four cylinders.
BLEEDING THE FUEL SYSTEM TYPE 108 ENGINES
BLEEDING THE FUEL SYSTEM
Fig. 11 ~`
Note: After renewing the
fuel filter element it will only be necessary to bleed the fuel filter as
described in 1 and 2, provided that the engine has not been cranked while the
filter is dismantled.
1 Slacken the blanking plug in the unused outlet connection in the fuel
filter head Fig. 12. Operate the lift pump Fig. 9 (page 5) until the fuel
flowing from the plug is free of air bubbles, tighten the plug. NB. Numbers
2-6 refer to Fig. 11 bleed points.
2 Slacken the union nut at the injection pump end of the fuel feed pipe.
Operate the lift pump and when the fuel flowing from the union is free
from air bubbles, tighten the nut.
3 Slacken the air bleed screw on the injection pump body. Operate the lift pump
and, when the fuel flowing from the bleed screw is free from bubbles, tighten the screw.
4 Slacken the air bleed screw on the injection pump governor housing.
Operate the lift pump until the fuel flowing from the bleed screw is free
from air bubbles, leave the bleed screw slack.
5 Slacken the air bleed screw on the injection pump high pressure banjo bolt.
Operate the starter motor while operating the throttle control and, when the
fuel flowing from the high pressure bleed screw is free of air bubbles,
tighten the bleed screw.
6 Co ntinue cranking the engine with the starter motor to expel any air
trapped in th e governor and, when the fuel flowing from the go vernor
housing bleed screw is free of air bubbles, tighten the screw.
Slacken the unions at the injector ends of any two high pressure pipes. Fig.
13. Ensure that the stop control is in the run position and the engine
speed control is in the fully open position. Crank the engine until the fuel
comibng from both pipes is free from air bubbles, then tighten the unions. NB. After initial
start procedure has been observed start the engine and allow it to idle until it is
running evenly on all four cylinders.
THORNYCROFT INITIAL START, NORMAL START, RUNNING IN
With all systems filled, primed and checked the engine may be started. Run it for
2 to 3 minutes then stop it. Top up engine, gearbox oil and water levels to the
high mark. The engine and gearbox are now ready for use. Oil pressure should be
observed within 15 seconds.
NORMAL STARTING PROCEDURE
1 Put gearbox selector lever in neutral.
2 Ensure the stop control is fully disengaged.
3 Set the engine speed control lever fully open.
4 Turn the key to 'H' position on starter switch and hold for 30 seconds (this
preheats the heater plugs). (This is not necessary for a warm engine.
Also control level only needs to be set half open).
5 Turn the key to 'H & S' position and the starter motor will crank up the
CAUTION: If the starter fails to crank up the engine within 10 seconds,
re lea se t he s wit ch k ey a nd w ait for th e starter motor to come to a
c o m pl et e st o p . T h en tu r n t h e k e y to 'H & S' po s i ti o n a ga i n. D o n o t
engage the starter motor for more than 30 seconds, then wait 2 minutes
between unsuccessful attempts.
6 Move the throttle position to idle as soon as engine starts.
7 Oil pressure should be observed within 15 seconds.
8 To stop the engine, pull the stop control.
The care given to an engine in the first 20 hours of operation will result in
longer life, better performance and more economical operation. During this
period follow these recommendations.
1 Warm up the engine before placing it under load.
2 Do not operate the engine at idle or full load for more than 5 minutes. 3 Avoid
4 Observe oil pressure and temperature gauges. 5
Check the oil and coolant levels frequently. GENERAL
1 NEVER attempt to start the engine with the gearbox control lever in any
position other than neutral.
2 NEVER stop the engine without first engaging neutral.
3 When changing the control lever from ahead to astern or vice versa pause in
I Page 8
COMPLIANCE WITH THE FOLLOWING RECOMMENDATIONS CAN RESULT IN LONGER LIFE, BETTER PERFORMANCE AND
MORE ECONOMICAL OPERATION OF YOUR ENGINE.
Routinely perform all of the specified maintenance, including the "First Start of
the Day" checks.
Use anti-freeze during all seasons to protect the cooling system from corrosion as well as
Never operate the engine without a thermostat.
Use quality fuel that is free of water and other contaminants. Monitor the oil
pressure and temperature indicators frequently. AVOID FULL THROTTLE
OPERATION WHEN THE ENGINE IS COLD.
When starting a cold engine, bring the engine up to operating speed slowly to
allow the oil pressure to stabilise as the engine warms up.
If temperatures are below 0°C (32°F), operate the engine at moderate speeds for 5 minutes before
full loads are applied.
AVOID IDLING THE ENGINE FOR MORE THAN 10 MINUTES
Long periods of idling may be harmful to your engine because combustion chamber temperatures can
drop so low that the fuel may not burn completely. Carbon can then form which may clog the
injector spray holes and also cause valves and piston rings to stick.
AVOID OVERHEATING THE ENGINE
Co ola nt t emp era tur e mu st not ex ceed 99 °C (210 °F) wi th a 70 kP a ( 10 p si)
expansion tank cap AND A MINIMUM OF 50% mixture of ethylene-glycol and water.
IDLE THE ENGINE A FEW MINUTES BEFORE ROUTINE SHUTDOWN
After full load operation, idle the engine 3 to 5 minutes before shutting it off
to allow th e lu bricating o il and coola nt to car ry h eat away from the
combustion chamber, bearings, shafts, etc.
AVOID LOW COOLANT TEMPERATURE OPERATION
Continual operation at l ow coo lant temperat ure be low 60°C ( 150°F) can be
harmful to the engine. Low coolant temperature can cause incomplete combustion
allowing carbon and varnish to form that can damage piston rings and injector
nozzles. A lso, th e unburnt fu el c an enter the crankcase di lut ing the
lubricating oil causing rapid wear to other moving parts.
THORNYCROFT OPERATING GUIDELINES
DO NOT OPERATE THE ENGINE WITH LOW OIL PRESSURE
When the engine is at normal operating temperature, the minimum oil pressures
Idle (570 RPM) ........................... 1 bar (15 psi)
Full Speed and Load .................... 2.3 bar (35 psi)
DO NOT OPERATE THE ENGINE WITH FAILED PARTS
Practically all failures give some warning before the parts fail. Be on the
alert for changes in performance, sounds and visual tip-offs that indicate
either service or repair is needed. Some important clues are:
Engine misfiring or vibrating severely
Sudden loss of power
Unusual engine noises
Fuel, oil or coolant leaks
Sudden change in the engine operating temperature Excessive
Loss of oil pressure
Saf ety i s bu ilt i nto eve r y en gin e; ho wev er, l ike any o the r
mechanical device, it can present serious threat to life and limb if
imprudently operated and maintained. Remember that the best
safeguards again st accidents are to kee p ever mindful of the
potential dangers and to always use good common sense.
MAINTENANCE SCHEDULE TH0RNYCROFT
DAILY OR EVERY 10 HOURS
Check engine and gearbox oil levels, top up if necessary. Check
coolant level and top up if necessary. Check drive belt
AFTER FIRST 25 HOURS
Retorque cylinder head nuts.
Change the engine oil and renew engine oil filter.
Check valve rocker clearances.
Check drive belt tensions
Check oil connections for leaks.
Check water hose connections.
Check all electrical equipment.
Change fuel filter element.
Check and service injectors as necessary.
Check and adjust engine idling speed as necessary (Use a Thornycroft dealer) Check fuel
system for leaks.
ENGINES IN REGULAR USE
EVERY 50 HOURS
Check electrolyte level in batteries.
EVERY 200 HOURS OR YEARLY
Change fuel filter element.
Change engine oil.
Change engine oil filter.
Check drive belts.
Check air cleaner and clean if necessary.
Check for oil or coolant leaks.
Check fuel system for leaks.
Check gearbox oil level.
Check and adjust idling speed as necessary.
EVERY 400 HOURS
In addition to the 200 hour maintenance schedules, change the gearbox oil. Remove heater
plugs and remove carbon from each orifice.
EVERY 800 HOURS
In addition to the 200 hour and 400 hour maintenance schedules Adjust valve
Test injectors for spray (Use a Thornycroft dealer)
Check all engine and gearbox connections. Renew oil
filler cap on rocker cover
ENGINES USED OCCASIONALLY HALVE THE HOURS RECOMMENDED AFTER FIRST 25 HOURS
THORNYCROFT ENGINE OIL CHANGE TYPE 90 ENGINES
CHANGE ENGINE OIL
Run the engine until it reaches normal operating temperature, stop the engine, then
using the hand pump Fig. 14 drain the oil into a suitable container.
CHANGE ENGINE OIL FILTER
Slacken the centre fixing bolt '1' Fig. 15 and
withdraw the filter bowl '2' and filter element
'3' together. Discard the filter element and
sealing ring '4'.
Replace with new element and sealing ring, ensuring that the ring is
correctly seated i n t he filt er head ' 5' and tig hte n t he centre bolt.
Fill the engine with the specified amount of oil and prime the oil system
as described on Page 4.
Start the engine and check for oil leaks, run the engine for 2 minutes
ensure pressure registers on the gauge. Stop the engine and allow a few
minutes for oil to settle. Check oil level, top up if necessary.
ENGINE OIL CHANGE TYPE 108 ENGINES THORNYCRO
FT Page 12
CHANGE ENGINE OIL
Run t he engine u ntil it reaches nor mal
operating temperature, stop the engine,
then using the hand pump Fig. 16 drain the
oil into a suitable container.
Unscrew the oil filter cartridge
Fig. 17. Discard the cartridge and
its sealing ring.
Lightly smear the sealing ring with clean
engine oil Fig. 18 and screw the filter
cartridge into place using hand pressure
only until the sealing ring abuts with the
filter head face. Then tighten a further
- a of a turn.
Fill the engine with the specified amount as
of oil and prime the oil system described on Page 4.
Start the engine and check for oil leaks, run the engine for 2 minutes ensure
pressure register on the gauge. Stop the engine and allow a few minutes for
Oil to settle, Check oil level and top op if necessary
THORNYCROFT FUEL FILTER CHANGE
RENE W FUE L FILTER ELE MENT
Turn off the fuel supply tap then support the filter base '1' Fig. 1 9 and unscrew
the centre bolt '2'. Detach the base and twist the element '3' to separate it from
the filter head '4'. Remove the three sealing rings '5' from the head and base.
Discard element and sealing rings. Clean base and head and assemble the filter
using a new element and sealing rings. Fit the element with its strengthened
rim uppermost. 'Turn on the fuel supply tap then bleed the air from the system as
described on Page 5 or 6.
CLEANING FUEL LIFT PUMP THORWC"T
FUEL LIFT PUMP FILTER
Turn off the fuel supply tap then remove the cap screw '1', Fig. 20. Lift off the cap '2',
gasket '3' and filter gauze '4'. Clean the gauze in a suitable solvent usin g a
sti ff brush. Clean the fuel cham ber '5'. Check that the gasket is serviceable
or renew. Assemble the components. Do not overtighten the cap screw. (Never
clean inside fuel chamber or any other part of the fuel system with a fluffy
cloth.) Turn on the fuel supply tap then bleed the fuel system as described on
Page 5 or 6.
THORNYCROFT GEARBOX OIL CHANGE
Page 1 5
CHANGING THE GEARBOX OIL
T he gearbo x o il must be changed when the gearbox has reached operating
temperature. (After about 1/2 hour driving the craft).
To help the oil drain easily from the gearbox first remove the oil filler
dipstick plug from the top of the gearbox. Place a suitable container under the
gearbox and remove the drain plug from the underside of the gearbox and allow
the oil to drain completely Fig. 21. The drain plug is in approximately
the same position on the underside of Hurth, Borg Warner and Newage PRM
Refit the drain plug. Fill the gearbox to the maximum mark on the dipstick.
Refit the filler plug, start the engine in neutral, and run the engine for 1
minute to allow the oil to circulate. Stop the engine and check the oil level.
Top up if necessary to the maximum mark on the dipstick.
Illustration shows PRM 160 gearbox
CLEANING AIR FILTER THORNYC
ROFT Page 16
CLEANING AIR FILTER
Slacken the clip on the breather pipe and pull the pipe off the air cleaner
then, slacken the screw Fig. 22 this allows removal of the outer casing and the air filter gauze.
Submerge the casing and gauze in a bath of clean paraffin or diesel fuel, agitate them
vigorously to remove dirt particles. Shake the filter dry by hand or blow dry with
compressed air, then refit.
CAUTION: WHEN USING A COMPRESSED AIR LINE GREAT CARE MUST BE OBSERVED AND
GOGGLES MUST BE WORN
THORNYCROFT DRIVE BELT ADJUSTMENT AND REPLACEMENT
ALTERNATOR AND RAW WATER PUMP
SAFETY: BEFORE ATTEMPTING THESE OPERATIONS
DISCONNECT THE STARTER BATTERIES Adjusting
Alternator Drive Belt
Type 90 alternator is shown in the
illustration Fig. 23 but procedure for
adjusting the alternator drive belt is
the same for type 108 engines.
Slacken the nuts and bolts 1-4. Move
alternator away from the engine until the
deflection of the belt (arrowed) is 19mm
(0.75 in) when pressed using finger pressure
only at the longest point between pulleys.
Excessive tension will cause early wear of
the belt, water pump bearing and
alternator bearing. While a slack belt
will slip, causing overheating of the
engine and insufficient charging of the
batteries. Check deflection after
Replacing Alternator Drive Belt
Slacken the nuts and bolts (Fig. 23) 1-4,
move alternator in towards engine. Remove
old belt from pulleys and replace with new
drive belt. Retighten nuts and bolts.
Following the instructions above readjust
the drive belt tension.
Adjusting Raw Water Pump Drive Belt
Slacken the nuts and bolts (Fig. 24) 1
and 2 an d ret ens ion the b elt as
described above for the alternator.
(The deflection of the belt must be
10-12mm 0.39-0.47in). Check deflection
Replacing Raw Water Pump Drive Belt
Slacken the nuts and bolts (Fig. 24) 1
and 2. Move pump in towards engine.
Remove old belt from pulleys and
replace with new drive belt.
Retighten nuts and bolts, following
the instructions above readjust the
drive belt tension.
CHECKING AND SETTING VALVE CLEARANCE
SAFETY: BEFORE ATTEMPTING THIS OPERATION DISCONNECT THE STARTER BATTERIES
Setting Valve Clearances Engine Cold
Slacken the rocker cover bolts and remove rocker cover. Discard the gasket. Turn
the crankshaft in the normal direction of rotation and adjust as follows.
Slacken the locknut and adjust with a screw driver until the correct clearance is
obtained. Fig. 25. Insert the feeler blade between the valve stem and rocker arm.
When correct adjustment is obtained the feeler blade is able to be removed with
Adjust in the following sequence:
Set No. 1 tappet with No. 8 valve fully open Set
No. 3 tappet with No. 6 valve fully open Set No.
5 tappet with No. 4 valve fully open S et No. 2
tappet with No. 7 valve fully open Set No. 8
tappet with No. 1 valve fully open Set No. 6
tappet with No. 3 valve fully open Set No. 4
tappet with No. 5 valve fully open Set No. 7
tappet with No. 2. valve fully open
Rec hec k the clearance wit h the loc knu ts
tightened and readjust if necessary.
Valve Clearance - Type 90 engines
Inlet Valve 0.381mm (0.015in)
Exhaust Valve 0.381mm (0.015in)
Valve Clearance - Type 108 engines Up
to Thornycroft Engine No. 6043 Inlet
and Exhaust 0.43mm (0.017in)
Engine No. 6043 onwards
Inlet and Exhaust 0.35mm (0.014in)
Fit the rocker cover using a new gasket. Tighten the bolts.
Reconnect the battery, start the engine and check the rocker cover for leaks.
THORNYCROFT PROCEDURE FOR RETORQUING CYLINDER HEAD NUTS
1 PROCEDURE FOR NEW ENGINES WHICH HAVE RUN FOR 25 HOURS
A Run engine and stop when normal operating temperature is reached.
B Slacken the cylinder head nuts by approximately 1/6" of a turn (one flat
of the nut) following the sequence shown using service tool 18G 1457
to reach the nuts in the centre row.
C Tighten the nuts in the sequence shown to 10.4 kgf m (75 lb ft).
11 6 5 12
00 00 0o
? 90 0 9 0 1 0 A
14 107 3 1 4 89
Slacken the valve rocker pedestal nuts by 1/6" of a turn (one flat of
the nut) and retorque to 3.5 kgf m (25 lb ft). Adjust valve rocker
clearances (Page 18).
2 PROCEDURE WHERE PART ENGINES HAVE BEEN FITTED OR WHERE CYLINDER HEADS ARE
REMOVED OR REPLACED DURING REPAIR OPERATIONS
A The cylinder head nuts should not be more than finger tight until the
rocker shaft assembly has been fitted.
Tighten the nuts to 10.4 kgf m (75 lb ft) type 108 engines, 9.8 kgf m
(.71 lb ft) type 90 engines in the sequence shown in procedure 1.
Using service tool 18G1457 to reach centre row. Fig. 27.
C Tighten the valve rocker pedestal nuts to 3.5 kgf m (25 lb ft).
D Adjust the valve rocker clearance as in procedure 1.
When the engine has run f or Y2 hour carr y out the operat ion descr ibed in
REMOVAL AND REFITTING FUEL INJECTORS THORNY
REMOVING FUEL INJECTORS
Injector cleaning and spray testing can only be carried out with specialised
equipment, therefore this must be done by a Distributor or Dealer.
Fig. 28. Disconnect the feed pipe '1' and spill rail '2'. Note the sealing
washers '3' on each side of the spill rail banjo union. Remove the injector
securing bolts '4' and withdraw the injector. Fit protective caps to all open
REFITTING FUEL INJECTORS
Remove protective caps. Ensure the washers are fitted to the injectors as
shown in Fig. 29. It is most important to tighten the injector fixings evenly and
to the correct torque of 1.65 kgf m (12 lbf ft), overtightening or uneven
tightening of the injector can distort the nozzle and will usually cause a
misfire to occur when normal running temperature is reached. Reconnect the
injector pipes, do not overtighten the unions.
TO REMOVE HEATER PLUGS AND CLEAN
ORIFICES. Disconnect the battery. Remove
electrical leads '1' Fig.29A and unscrew
each plug '2' from th e cylinder head.
Insert a twist drill of 4.37mm
(11 /64 in) dia. '3' into t he th rea ded
holes in the head '4'. Turn the drill, by
han d, to r emo ve car bon bui ld- up.
Remove the drill and clean any particles of
carbon from conical seatings in the
cylinder head. Refit the heater plugs
and e lec tri cal l ead s. Re connec t the
TAT CHANGING COOLANT
Remove filler cap from heat exchanger, place a suitable container beneath the drain plug
Fig. 30. Remove plug and allow to drain.
Place suitable container beneath drain tap in cylinder block Fig. 31.
tap and allow to drain.
Replace both plug and tap then refill with coolant of the correct strength for conditions
to be encountered. See Page. 3.
DRAINING RAW WATER SYSTEM
DRAIN THE RAW WATER SYSTEM
Slacken the six screws Fig.32 on the raw water pump. Remove end covers from
heat exchanger and drain tubes either by removing the tube stack or by blowing out
with compressed air. Remove oil cooler and drain tubes or blow out with
compressed air. Alternatively disconnect raw water pipework before gearbox oil
cooler and pipe from oil cooler into a container of anti-freeze mixture and
flush through system returning anti-freeze mixture from water injection bend
back into container, this ensuring that any water pockets contain anti-freeze.
CAUTION: WHEN USING A COMPRESSED AIR LINE GREAT
CARE MUST BE OBSERVED AND GOGGLES MUST BE
NOTE: ANTI-FREEZE MIXTURE MUST BE OF CORRECT STRENGTH FOR CONDITIONS TO BE
ROUTINE MAINTENANCE OF RAW WATER SYSTEM IFWC
THESE NOTES DO NOT APPLY TO EXTERNAL FRESH WATER COOLED ENGINES
Examine and clean the sea inlet strainer at regular intervals. Do Not remove the
strainer when the engine is running as foreign matter can be drawn into the system and cause
irreparable damage to the pump. The sea cock must be FULLY OPEN when the engine
is running. If the sea cock is partially closed, air can be drawn in with
consequ ential failure of the raw water pump and engine overheating. Check the
raw water discharge pipe immediately after starting the engine to see if the raw water
pump is functioning.
The engine MUST NOT run without a flow of raw water through the heat exchanger.
RAW WATER PUMP, the raw water pump is self priming and fitted with a neoprene
impellor. It depends on the raw water for its lubrication. DO NOT run dry.
M ore than 3 0 se con ds runn ing withou t wate r will b urn the impellor and be
contributory to an early failure. When replacing the end cover gasket, it is
essential to use the correct part; variation of the gasket thickness can cause loss of'self
priming ability or seizure.
EXTERNAL FRESH WATER COOLED ENGINES ONLY (EFWC)
Page 2 3
This consists of a closed circ uit fresh water system with a fre sh water
circulator, combined header tank and exhaust manifold, dry exhaust outlet and
water/coolant tanks normally fitted to the skin of the craft. It is therefore
important when filling this system with anti-freeze solution or corrosion
inhibitor that the total capacity of the tanks, associated pipework and the
engine cooling system is taken into consideration. Your boat builder will
advise you on these figures.
We have included the box below for you to fill in these figures for your craft.
Name of Craft External Fresh Water Cooled System
Capacity Date Change Due
ELECTRICAL SYSTEM THORNYCROFT
An insulated return system is employed on the type 90 and 108 engines.
The 12 volt alternator has a built-in voltage regulator which automatically
adjusts the charging rate to provide sufficient electric current to keep the
battery fully charged under normal operating conditions.
The alternator requires no lubrication maintenance.
Do NOT disconnect the battery leads while the engine is running.
Ensure that the correct battery terminal is connected to a good earth on the
A coating of a good grade of petroleum jelly will protect the terminals from
The electrolyte level should be 6 to 9mm (0.25 to 0.38in) above the top of the plates. If the
electrolyte is below the correct level, add the required amount of distilled
Distilled water for battery use should be kept in clean, covered, non-corrodible
vessels. In cold weather, add water only immediately before running the engine, so
that the charging will mix the water and electrolyte and prevent freezing.
If t he b att ery i s al lowed to sta nd at lo w tem per atu res in a p art ial ly
discharged condition there is a possibility that it may freeze, causing damage to the container. Take
care therefore, to keep the battery as fully charged as possible.
The specific gravity of the electrolyte when the battery is fully charged
should be 1,275 at a temperature of 25°C (77°F). At differing temperatures the specific gravity
of a fully charged battery will change. The specific gravity of any given temperature
can be calculated by subtracting 0.004 from 1,275 for every 6°C change above 25°C and adding 0.004 to
1,275 for every 6°C below 25°C.
Keep the battery filler plugs and connections tight and the top of the battery clean. Wiping
the battery with a rag moistened with ammonia will counteract the effect of any
of the solution which may be on the outside of the battery. Wear protective
goggles when carrying out this operation. If ammonia is accidentally splashed in the
eyes, wash out thoroughly at once with clean water and SEEK QUALIFIED MEDICAL ADVICE
Using 'Jumper' Cables
To avoid the possibility of extensive damage to your charging system it is
important to observe the following points when using battery 'jumper' cables to start an engine
having a discharged battery. The positive (+) terminals of the batteries must be connected
through one cable (usually red), and the negative (-) terminals connected
through the other cable. If this procedure is not followed, extensive damage may be
done to the charging system.
CAUTION: Since explosive hydrogen gas is always present, sparks or flames
should not be allowed near the battery. When using 'jumper' cables, the
cables should always be attached to the booster battery first.
THORNYCROFT FAULT FINDING
ENGINE WILL NOT START
Starter does not ELECTRICAL FAULT
crank engine Battery run down
Faulty starter switch
Faulty starter motor
Starter cranks ELECTRICAL FAULT
engine slowly Battery partly run down
Connections dirty Faulty
Wrong grade engine oil
Starter cranks ELECTRICAL FAULT
engine normally Faulty glow plugs
Faulty wiring connection
Injection timing incorrect
Poor cylinder compression
Blocked air intake
Fuel Not Reaching
Injection Pump Insufficient fuel in tank
Blocked fuel pipeline
Blocked fuel tank vent
Restricted fuel filter Air
leaks in pipeline
Injection Pump Air in fuel system