.
Chapter Six
GM Inline Engines
This chapter covers the GM 153 and 181 cid
4-cylinder engines and the GM 194, 230, 250 and
292 cid 6-cylinder inline engines used on
MerCruiser 110 through 200 models. Although
differing in displacement, these engines are
essentially the same design with many
interchangeable parts.
These engines are used with the following
MerCruiser models:
a. Model 110, 120, 120R and 120MR-153
cid.
b. Model 140-181 and 194 cid.
c. Model 140R and 140MR- 181 cid.
d. Model 150-230 cid.
.
e. Model 160 and 165-250 cid.
f. Model 200-292 cid.
The cylinders are numbered from front to rear:
l-2-3-4 (6cylinder) and l-2-3-4-5-6 (6-cylinder).
Engine firing order is also standard: l-3-4-2
(Ccylinder) and l-5-3-6-2-4 (6-cylinder).
Rocker arms are retained on individual threaded
studs. A ball pivot valve train is used, with
camshaft motion transferred through the hydraulic
lifters to the rocker arms by pushrods.
The 4-cylinder crankshaft may be supported by 4
or 5 main bearings; the 6-cylinder crankshaft has 7
main bearings. The rear bearing on each takes the
end thrust. Crankshaft rotation is counterclockwise
when seen from the drive unit end of the engine.
The gear-driven camshaft is supported by 4
bearings and is located above the crankshaft in the
engine block.
The oil pump is located on the bottom front of
the block on the starboard side and is driven by the
distributor shaft. The distributor is driven by a gear
on the camshaft.
Specifications (Table 1 and Table 2) and
tightening torques (Table 3) are at the end of the
chapter.
ENGINE SERIAL NUMBER
The engine serial number is stamped on a plate
mounted on the right rear side of the engine block
above the starter motor (Figure 1).
This information identifies the engine and
indicates if there are unique parts or if internal
changes have been made during the model run. It is
important when ordering replacement parts for the
engine.
SPECIAL TOOLS
Where special tools are required or
recommended for GM engine overhaul, the tool
numbers are provided. Mercury Marine tool part
numbers have a “C” prefix. GM tool part numbers
have a “J” prefix. While GM tools can sometimes
be rented from rental dealers, they can be
purchased from Kent-Moore, Inc., 28635 Mound
Road, Warren, MI 48089.
GM INLINE ENGINES
REPLACEMENT
105
PARTS
Various changes are made to automotive engine
blocks used for marine applications. Numerous
part changes are required due to operation in fresh
and salt water. For example, the cylinder head
gasket must be corrosion-resistant. Marine engines
use head gaskets of copper’ or stainless steel instead
of the standard steel used in automotive
applications. Brass expansion or core plugs must be
used instead of the steel plugs found in automotive
blocks.
Since marine engines are run at or near
maximum rpm most of the time, the use of special
valve lifters, springs, pistons, bearings, camshafts
and other heavy-duty moving components is
necessary for maximum life and performance.
For these reasons, automotive-type parts should
not be substituted for marine components. In
addition, Mercury recommends
that only
Quicksilver parts be used. Parts offered by other
manufacturers may look alike, but may not be
01
SERIAL
NO.
LOCATION
manufactured to Mercury’s specifications. Any
damage resulting from the use of other than
Quicksilver parts is not covered by the Mercury
Marine warranty.
ENGINE
REMOVAL
Some service procedures can be performed with
the engine in the boat; others require removal. The
boat design and service procedure to be performed
will determine whether the engine must be
removed. In some installations, it may be
necessary to remove the stern drive unit first. See
Chapter Fourteen.
WARNING
The engine is heavy, awkward to handle and has
sharp edges. It may shift or drop suddenly during
removal. To prevent serious injury, always
observe the following precautions.
1. Never place any part of your body where a
moving or falling engine may trap, cut or crush
you.
2. If you must push the engine during removal,
use a board or similar tool to keep your hands
out of danger.
3. Be sure the hoist is designed to lift engines
and has enough load capacity for your engine.
4. Be sure the hoist is securely attached to safe
lifting points on the engine,
5 . The engine should not be dtJicult to lift with a
proper hoist. If it is, stop lifting, lower the engine
back onto its mounts and make sure the engine
has been completely separated from the boat.
1. Remove the engine hood cover and all panels
that interfere with engine removal. Place to one
side out of the way.
2. Disconnect the negative battery cable, then the
positive battery cable. As a precaution, remove the
battery from the boat.
3. Disconnect the throttle cable at the carburetor
(Figure 2). If necessary, remove cable from anchor
plate.
4. Disconnect the engine-to-instrument panel
wiring harness.
5. Disconnect the fuel lines at the fuel pump
(Figure 3). Plug the fuel lines to prevent leakage.
6. Disconnect the brown and black (shift interlock)
wires from the shift plate terminal block.
7. Disconnect the red and black power trim pump
motor wires at the engine.
8. Disconnect the trim indicator sender wires (if so
equipped).
CHAPTER SIX
106
9. Disconnect the water inlet hose. Open the
engine drain valve(s) and drain all water from the
block.
10. Disconnect the exhaust elbow bellows.
11. Disconnect the drive unit shift cable from the
J-clamp on the flywheel housing.
12. Disconnect the intake manifold vacuum hose,
if so equipped.
13. Disconnect any accessories connected to the
engine that will interfere with removal.
14. Attach a lifting bracket to the engine lifting
eyes. Connect the bracket to an engine hoist and
elevate it enough to remove all slack.
NOTE
At this point, there should be no hoses, wires or
linkage connecting the engine to the boat or
stern drive unit. Recheck this to make sure
nothing will hamper engine removal.
ENGINE MOUNTING
BRACKET PARTS
::
I
II
-
7$
15. Remove the front and rear engine mounting
bolts.
16. Slide the engine forward sufficiently to
disengage it from the drive shaft assembly.
17. Remove the engine from the boat with the
hoist.
ENGINE
Special split
lockwasher
ALarge fiber washer
/
INSTALLATION
Engine installation is the reverse of removal,
plus the following.
1. Coat the engine coupling splines with Universal
Joint Lubricant (part No. C-92-74058).
2. It may be necessary to rotate the crankshaft
slightly to align the engine coupling splines with the
drive shaft. You may also rotate the drive shaft by
placing the outdrive in forward gear and rotating
the propeller.
3. Install the front engine mount bracket.
4. Position a large fiber washer on top of the inner
transom plate mounting brackets. Position the
special split lockwasher inside the fiber washer. See
I
Mount bolt
Steel washer
-
t
.
Spacer
\I
Figure 4.
5. Position engine over the transom plate
mounting brackets. Install hose clamps over the
rubber exhaust elbow bellows, then fit bellows over
the exhaust manifold outlet and tighten the clamps
securely. See Figure 5.
CA UTION
Elastic stop nuts should never be used more than
twice. It is a good idea to replace such nuts with
new ones each time they are removed. Never use
worn-out stop nuts or non-locking nuts.
I
.. .
mina;‘usr
*UBE
II
6. Install steel washers and spacers on the
mounting bolts, then insert bolts down through the
rear engine mounts, washers and mounting
brackets. See Figure 5. Install elastic stop nuts on
bolts and tighten to specifications (Table 3).
GM INLINE ENGINES
107
THROTTLE CABLE
Wide open throttle
stop adjusting screw
engine with the hoist as required to permit
indexing with no resistance.
9. Tighten all fasteners to specifications (Table 3).
Remove the alignment tool.
10. Refer to Figure 7 and connect the throttle cable
as follows:
a. Move remote control to neutral gear, idle
position.
b. Connect cable end guide to throttle lever with
flat washer and nut.
c. Holding throttle cable behind the brass barrel,
push it toward the throttle lever. Adjust
barrel to align with anchor stud, then connect
barrel to stud with flat washer and nut.
d. Make sure throttle valves are wide open when
remote control is in full-forward position,
then turn wide-open throttle stop adjusting
screw clockwise until it just touches the
throttle lever.
e. Tighten set nut securely, return control to
neutral gear, idle position and make sure that
idle stop screw rests against the stop.
11. Fill the engine with an oil recommended in
Chapter Four.
12. Fill the cooling system, if equipped with a
closed system. See Chapter Twelve.
13. Adjust the drive belts. See Chapter Thirteen.
DISASSEMBLY
Brass barrel
7. Turn adjusting nuts in front mounting bracket
until bracket rests solidly on the mount location in
the boat. See Figure 6. Install mount to boat.
CAUTION
If the alignment tool specified in Step 8 is not
available, take the boat to a MerCruiser dealer
for proper alignment. Drive shaft/coupling spline
misalignment can cause serious damage.
8. Coat the solid end of alignment tool part No.
C-9 l-48247 with multipurpose lubricant and insert
it from outside the boat through the gimbal
bearing. Index the bearing and drive shaft with the
engine coupling splines. If indexing is difficult,
loosen the front mount and raise or lower the
CHECKLIST
To use the checklists, remove and inspect each
part in the order mentioned. To reassemble, go
through the checklists backwards, installing the
parts in order. Each major part is covered under its
own heading in this chapter, unless otherwise
noted.
Decarbonizing or Valve Service
1. Remove the rocker arm cover.
2. Remove the intake and exhaust manifolds.
3. Remove the rocker arm assembly.
4. Remove the cylinder head.
5. Remove and inspect the valves. Inspect valve
guides and seats, repairing or replacing as required.
6. Assemble by reversing Steps l-5.
Valve and Ring Service
1. Perform Decarbonizing or Valve Service.
2. Remove the oil pan.
3. Remove the pistons with the connecting rods.
CHAPTER SIX
108
4. Remove the piston rings. It is not necessary to
separate the pistons from the connecting rods
unless a piston, connecting rod or piston pin needs
repair or replacement.
5. Assemble by reversing Steps 1-4.
General Overhaul
1. Remove the engine from the boat.
2. Remove the flywheel.
3. Remove the engine mount brackets and oil
pressure sending unit from the engine.
4. If available, mount the engine on an engine
stand. These can be rented from equipment rental
dealers. The stand is not absolutely necessary, but
it will make the job much easier.
5. Check the engine for signs of coolant or oil
leaks.
6. Clean the outside of the engine.
7. Remove the distributor. See Chapter Thirteen.
8. Remove all hoses and tubes connected to the
engine.
9. Remove the fuel pump. See Chapter Eleven.
10. Remove the intake and exhaust manifolds.
11. Remove the thermostat. See Chapter Twelve.
12. Remove the rocker arm assemblies.
13. Remove the crankshaft pulley/vibration
damper and timing case cover. Remove the timing
gear and sprockets.
14. Remove the camshaft.
15. Remove the seawater pump, if so equipped.
See Chapter Twelve.
16. Remove the cylinder head.
17. Remove the oil pan and oil pump.
18. Remove the pistons and connecting rods.
19. Remove the crankshaft.
20. Inspect the cylinder block.
2 1. Assemble by reversing Steps l- 19.
ROCKER ARM COVER
Removal/Installation
1. Remove the crankcase vent line(s) from the
rocker arm cover (Figure 8).
2. Unclip or detach any wires or wire looms
attached to the rocker arm cover.
3. Disconnect the fuel line at the carburetor
(Figure 9). Plug the line to prevent leakage.
4. Remove the cover attaching screws. Tap the
rocker arm cover with a plastic mallet to break the
gasket seal. Remove the rocker arm cover.
5. Clean any gasket residue from the cylinder head
and rocker arm cover with degreaser and a putty
knife.
6. Coat one side of a new gasket with an
oil-resistant sealer and install sealer-side down in
the rocker arm cover. Gasket tabs must engage
cover notches.
7. Install the cover on the cylinder head.
8. Install the attaching screws and tighten to
specifications (Table 3).
9. Install the crankcase vent line in the rocker arm
cover (Figure 8).
INTAKE/EXHAUST
MANIFOLDS
The intake and exhaust manifolds are combined
in one unit. Figure 10 shows a typical exhaust
manifold assembly.
109
GM INLINE ENGINES
10
3
EXHAUST MANIFOILD
(TYPICAL)
1. Bolt
2 . Washer
3. Screw
4 . Nut
5 . Washer
0. Bolt
7. Front end cap
8 . Gasket
9. Exhaust heat tube
lg. Stud
11. Gasket
12. Plug
13. Water drain plug
14. Lockwasher
15. Nut
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
Exhaust elbow
Water separation tube
Gasket
Stud
Exhaust manifold
Gasket
Rear end cap
Bolt
Drain plug
Plug
Wiring harness clamp
Lockwasher
screw
Plug
Removal/Installation
1. Disconnect the negative battery cable.
2. Open the cylinder block water drain(s) and
allow all water to drain.
3. Disconnect the throttle cable at the carburetor
and remove the return spring.
4. Remove the manifold cooling hose(s) at the
thermostat housing (Figure 11).
5. Disconnect the exhaust hose. Drain any water
remaining in the manifold housing and elbow.
6. Disconnect the fuel line at the carburetor. Plug
the line to prevent leakage.
7. Disconnect the crankcase vent line(s) at the
rocker arm cover (Figure 8).
CHAPTER SIX
110
8. Remove the wiring harness clamps at the
manifold.
9. Unbolt alternator bracket from manifold
(Figure 12).
10. Remove manifold assembly fasteners and
washers. Remove the manifold assembly with
carburetor attached. Discard .the manifold gasket.
11. Separate the manifolds, if required.
12. Clean all gasket residue from the cylinder head
and manifold mating surfaces with degreaser and a
putty knife.
13. Combine manifolds, if separated in Step 11,
and install on cylinder head with a new gasket.
Tighten fasteners to specifications (Table 3)
working from the center to the ends. The
remainder of installation is the reverse of removal.
Intake
Manifold
Inspection
1. Remove carburetor from manifold. Check
manifold for cracks or distortion. Replace as
required.
2. Check mating surfaces for nicks or burrs. Small
burrs may be removed with an oilstone.
3. Place a straightedge across the manifold mating
surface. If there is any gap between the mating
surface and straightedge, measure it with a feeler
gauge. Measure from end to end and comer to
comer.
4. The mating surface should be flat within 0.006
in. per foot of manifold length. If not, replace the
manifold.
GM INLINE ENGINES
111
Exhaust Manifold
Inspection/Cleaning
1. Inspect engine exhaust ports for signs of rust or
corrosion. Replace manifold if such signs are
found.
2. Check water passage in exhaust elbow for
clogging.
3. Check inside of exhaust hose for signs of
burning. Replace if burning is noted.
CRANKSHAFT
CRANKSHAFT PULLEY HUB REMOiAL
Pulley
PULLEY/TORSIONAL
DAMPER
Removal/Installation
1. Remove alternator drive belt. See Chapter
Thirteen.
2. Remove pulley attaching bolts (Figure 13).
Remove pulley from hub.
3. Install puller part No. J-6978 to pulley hub with
pulley attaching bolts and remove hub. See Figure
14.
TORSIONAL DAMPER REM&VAL
4. Lubricate timing gear cover seal lip with clean
engine oil.
5. Position hub on crankshaft end and start with a
mallet, then use tool part No. J-5590 to strike the
hub until it is fully seated against the crankshaft
gear. Crankshaft will extend through the hub
slightly when bottomed.
6. Install and adjust alternator drive belt. See
Chapter Thirteen.
Torsional Damper
Removal/Installation
TORSIONAL DAMPER INSTALLATION
1. Remove alternator drive belt. See Chapter
Thirteen.
2. Install puller part No. J-6978 to torsional
damper and remove damper. See Figure 15.
3. Lubricate timing gear cover seal lip with clean
engine oil.
4. Install tool part No. J-8792 to damper (Figure
16), place damper and tool against crankshaft and
drive onto the crankshaft until fully seated.
Remove tool.
CHAPTER SIX
112
5. Install and adjust alternator drive belt. See
Chapter Thirteen.
TIMING GEAR COVER AND SEAL
Removal/Installation
This procedure can generally be performed
without removing the engine from the boat,
provided you are careful in cutting the oil pan seal
in Step 4.
1. Remove the crankshaft pulley/hub or torsional
damper as described in this chapter.
2. Remove the 2 screws holding the front of the oil
pan to the timing gear cover (bottom arrows,
2. Place cover on a clean flat workbench surface.
3. Pry old seal from cover with a screwdriver.
4. Clean the seal recess in the cover with solvent
and blow dry.
5. Position new seal in cover recess with open end
of seal facing cover. Support cover at seal area and
drive seal into place with tool part No. J-23042.
6. Install timing gear cover as described in this
chapter.
Figure 17).
3. Pull the timing gear cover slightly away from
the block.
4. Use a sharp X-acto knife to cut the oil pan seal
flush with the cylinder block face.
5. Remove the timing gear cover bolts. See Figure
17. Remove the cover, cover gasket and cut portion
of the oil pan seal. Discard the cover gasket. Keep
the pan seal segment for use as a template in Step 8.
6. Clean the gasket mounting surfaces on the block
and cover with degreaser and a putty knife.
7. Coat the gasket surfaces of the block and timing
gear cover with Perfect Seal (part No. C-92-34227)
or equivalent and install a new gasket on the block.
8. Use the cut portion of the oil pan seal as a
template and cut a matching section from a new
seal for use in Step 9.
9. Install the cut portion of seal to the bottom of
the timing gear cover, inserting the seal tips into
the cover holes.
10. Apply a l/8 in. bead of room temperature
vulcanizing (RTV) sealer along the joint on each
side where the oil pan meets the block.
Il. Install alignment tool part No. J-23042
through the timing gear cover seal. Position the
timing gear cover on the engine block. Work
carefully to prevent damage to the oil seal or
movement of the gaskets.
12. Apply upward pressure on the oil pan and
install the pan attaching screws.
13. Install the cover attaching bolts. Tighten cover
bolts and oil pan screws to specifications (Table 3).
14. Remove the alignment tool and install the
crankshaft pulley/hub or torsional damper as
described in this chapter.
Seal
Replacement
1. Remove timing gear cover as described in this
chapter.
Pushrod
retainer
qocker
arm stud
GM INLINE ENGINES
w
19
CAMSHAFT LOBE LIFT
MEASUREMENT
113
4. Install the pushrods, making sure that each fits
into its lifter socket.
5. Install the rocker arms, balls and nuts.
6. Adjust the valves as described in this chapter.
7. Install the rocker arm cover as described in this
chapter.
Inspection
1. Clean all parts with solvent and use compressed
air to blow out the oil passages in the pushrods.
2. Check each rocker arm, ball, nut and pushrod
for scuffing, pitting or excessive wear. Replace as
necessary.
3. Check pushrods for straightness by rolling them
across a flat, even surface such as a pane of glass.
Replace pushrods that do not roll smoothly.
4. If a pushrod is worn from lack of lubrication,
replace the corresponding lifter and rocker arm as
well.
CAMSHAFT
Lobe Lift Measurement
ROCKER ARM ASSEMBLIES
Removal/Installation
Each rocker arm moves on its own pivot ball.
The rocker arm and pivot ball are retained by a
nut.
It is not necessary to remove the rocker arm for
pushrod replacement; simply loosen the nut and
move the arm away from the pushrod. Refer to
Figure 18 for the complete removal procedure.
1. Remove the rocker arm cover as described in
this chapter.
2. Remove each rocker arm nut, ball, rocker arm
and pushrod.
3. Place each rocker arm/pushrod assembly in a
separate container or use a rack to keep them
separated for reinstallation in the same position
from which they were removed.
NOTE
When installing new valve lifters, rocker arms or
rocker arm balls, coat the contact surfaces with
engine oil or Molykote.
Camshaft lobe lift can be measured with the
camshaft in the block and the cylinder heads in
place. The lifters must be bled down slowly or the
readings will be incorrect.
1. Remove the rocker arm covers as described in
this chapter.
2. Remove the rocker arm assemblies as described
in this chapter.
3. Remove the spark plugs.
4. Install a dial indicator with a ball socket adapter
to fit over the pushrod. See Figure 19.
5. Turn the crankshaft in the normal direction of
rotation until the valve lifter seats on the heel of
the cam lobe. This positions the pushrod at its
lowest point.
6. Zero the dial indicator, then slowly rotate the
crankshaft until the pushrod reaches its maximum
travel. Note the indicator reading and compare to
specifications (Table 1 or Table 2).
7. Repeat Steps 4-6 for each pushrod. If all lobes
are within specifications, reinstall the rocker arm
assemblies and adjust the valves as described in
this chapter.
8. If one or more lobes are worn beyond
specifications, replace the camshaft as described in
this chapter.
9. Remove the dial indicator and reverse Steps
1-3.
CHAPTER SIX
114
Removal/Installation
1. Crank the engine over until the No. 1 piston is
at the top of its compression stroke. The timing
mark on the pulley/damper will align with the
TDC mark on the timing gear cover and the
distributor rotor will point to the No. 1 spark plug
terminal in the distributor cap. Remove the
distributor. See Chapter Thirteen.
2. Remove the rocker arm cover as described in
this chapter.
3. Remove the timing gear cover as described in
this chapter.
4. Remove the fuel pump. See Chapter Eleven.
5. Remove the rocker arm assemblies as described
in this chapter.
6. Remove the pushrod covers (Figure 20) and
discard the gaskets.
7. Remove the valve lifters and place in a rack or
other container in the order removed so they may
be reinstalled in their original locations. Figure 21
shows lifter location, with one lifter removed.
8. Rotate the camshaft to align the timing gear
marks (Figure 22).
9. Working through the access holes in the
camshaft gear, remove the 2 camshaft thrust plate
screws. See Figure 23.
10. Carefully withdraw the camshaft from the
front of the engine to avoid damage to the bearings.
11. Installation is the reverse of removal. Coat the
camshaft lobes with Lubriplate or equivalent and
the journals with heavy engine oil before
reinstalling in the block. Check gear run-out and
backlash as described in this chapter.
Inspection
1. Check the journals and lobes for signs of wear or
scoring. Lobe pitting in the toe area is not sufficient
reason for replacement, unless the lobe lift loss is
excessive.
2. Check each valve lifter for signs or wear, pitting
or scoring. Replace as required.
NOTE
Zf you do not have precision measuring
equipment, have Step 3 done by a machine
shop.
3. Measure the camshaft journal diameters with a
micrometer (Figure 24). If any journal exceeds
0.001 in. out-of-round, replace the camshaft.
,
115
GM INLINE ENGINES
4. Suspend the camshaft between V-blocks and
check for warpage with a dial indicator. See Figure
25. Replace if reading is greater than 0.002 in.
5. Check the distributor drive gear for excessive
wear or damage.
6 . Check camshaft gear and thrust plate for wear or
damage. Insert a feeler gauge between the thrust
plate and camshaft to measure end play. See Figure
26. If end play exceeds 0.005 in., remove the
camshaft gear as described in this chapter and
replace the thrust plate.
6
026
024
CAMSHAFT END PLAY MEASUREMENT
Camshaft
thrust plate
Camshaft gear
\
CHAPTER
116
Camshaft/Crankshaft
Gear
Runout and Backlash
27
n
SIX
TIMING GEAR RUNOUT
1. Install a dial indicator as shown in Figure 27.
Rotate camshaft 360’ to check runout. If camshaft
gear runout exceeds 0.004 in., replace the gear.
2. Reposition the dial indicator so its contact
plunger touches the face of. the crankshaft gear.
Repeat Step 1. If runout exceeds 0.003 in., replace
the gear.
3. Install dial indicator as shown in Figure 28 to
check gear teeth backlash. If backlash is not
between 0.004-0.006 in., replace both gears.
Bearing
Replacement
Camshaft bearings can be replaced without
complete
engine
Camshaft
disassembly.
bearing/installer tool part No. J-6098 is required
for bearing replacement.
1. Remove the camshaft as described in this
chapter.
2. Remove the crankshaft as described in this
chapter.
3. Drive the camshaft rear plug from the cylinder
block.
4. Secure the connecting rods to the side of the
engine to keep them out of the way while replacing
the cam bearings.
5. Install the nut and thrust washer to tool part No.
J-6098. Index the tool pilot in the front cam
bearing. Install the puller screw through the pilot.
6. Install tool part No. J-6098 with its shoulder
facing the front intermediate bearing and the
threads engaging the bearing.
7. Hold the puller screw with one wrench. Turn
the nut with a second wrench until the bearing has
been pulled from its bore.
8. Repeat Steps 5-7 to remove the center bearing.
9. Remove the tool and index it to the rear bearing
to remove the rear intermediate bearing from the
block.
10. Remove the front and rear bearings by driving
them toward the center of the block.
CAUTION
Improper rear bearing alignment in Step I I will
restrict oil pressure reaching the valve train.
11. Installation is the reverse of removal. Use the
same tool to pull the new bearings into their bores.
Bearing oil holes must align with those in the
block. Since the oil hole is on the top of the
bearings (and cannot be seen during installation),
align bearing oil hole with hole in bore and mark
opposite side of bearing and block at bore to assist
in positioning the oil hole during installation.
12. Wipe a new camshaft rear plug with Perfect
Seal (part No. C-92-34227) and install it flush to
l/32 in. deep to maintain a level surface on rear of
block.
Timing Gear Replacement
If inspection indicates that the camshaft, gear or
thrust plate should be replaced, press the gear from
the camshaft with an appropriate size support
sleeve. Position the thrust plate so that it will not
be damaged by the Woodruff key in the shaft when
it separates from the gear. If the gear is to be
reused, support its hub before applying pressure or
it will be ruined. Install the camshaft gear by
pressing it onto the shaft, then check end play as
described in Step 6, Inspection in this chapter.
’
GM INLINE ENGINES
117
b. Gaskets with insufficient crush (contact) in
certain areas to make a good seal.
c. Defective or improperly installed seals.
d. Mid-machining of the crankshaft and/or
block.
On installations manufactured after October
1985, GM used RTV sealant on the oil pan gaskets
and end seals. This was replaced in January 1986
by a new 2-piece “high-swell” gasket which
expanded when exposed to oil. In May 1986, a
1 -piece silicone rubber gasket (Figure 29)
,s :
superseded all previous gaskets. The soft rubber ;’ ;,’ gf
2 *y ;
fills in small gaps that might otherwise leak; metal : ‘: ;= s%
spacers around each of the screw holes prevent
damage from overtightening. The l-piece silicone
gasket should be used as a replacement whenever
the oil pan is removed from earlier models.
If oil leakage continues to be a problem after
installation of the new gasket (part No.
27-14901Al), remove the engine from the boat.
Remove the oil pan and measure at the following
areas:
TIMING GEAR BACKLASH
cer
a. Crankshaft diameter at the seal area. It should
be 2.43-2.432 in.
b. Inside diameter of the seal shoulder. It should
be 2.775-2.778 in.
If the measurements are not within the
specifications provided, the crankshaft and/or
block were incorrectly machined. See your
MerCruiser dealer.
Removal
1. Remove the engine as described in this chapter.
2. Place a 6-quart container under the oil pan
drain plug. Remove the plug and let the crankcase
drain.
OIL PAN
Oil Leaks
Constant oil leakage around the oil pan can be
caused by 1 of several factors:
a. Excessive torquing of the oil pan screws. This
squeezes the 2-piece gasket out and causes the
rubber end seals to split.
NOTE
A modification kit is available from marine
dealers to assist in draining the oil when the
engine is in the boat. This kit can be installed on
any engine oil pan when the engine is removed
for service.
3. If mounted in an engine stand, rotate the engine
180’ to place the oil pan in an upright position.
4. Remove the oil pan attaching screws. Remove
the oil pan.
5. Remove and discard the pan gasket and the
front/rear seals, if used.
CHAPTER SIX
118
Inspection
1. Remove all gasket residue from the oil pan
flanges and crankcase side rails with degreaser and
a putty knife.
2. Clean the pan thoroughly in solvent.
3. Check the pan for dents or warped gasket
surfaces. Straighten or replace the pan as necessary.
Installation
1. Install a new l-piece gasket on the pan flanges.
Insert a screw on each side and at each end of the
pan to position the gasket.
2. Carefully position the oil pan in place, make
sure the gasket is not misaligned and tighten the
screws inserted in Step 1 finger-tight.
3. Install the remaining screw and tighten all to
specifications (Table 3). Work from the center
outward in each direction.
4. Install the engine in the boat as described in this
chapter and fill the crankcase with oil
recommended in Chapter Four.
OIL PUMP
Removal/Installation
1. Remove the oil pan as described in this chapter.
NOTE
The oil pump pickup tube and screen are a press
jit in the pump housing and should not be
removed unless replacement is required.
2. Loosen the pickup tube bracket bolt (A, Figure
30). Remove bracket attaching nut (B, Figure 30).
3. Remove the oil pump attaching bolts (Figure
31). Remove the oil pump. gasket and pickup
tube/screen as an assembly.
4. To install, align the pump gear shaft slot with
the distributor shaft drive tang.
5. Install pump to block. Tighten pump attaching
bolts to specifications (Table 3).
6. Install the oil pan as described in this chapter.
2. Mark gear teeth to assure reassembly with
identical gear indexing and remove idler and drive
gear with shaft from the body.
3. Remove pressure regulator valve pin, regulator,
spring and valve.
4. Oil all parts thoroughly before reassembly.
5. Assembly is the reverse of disassembly. Index
gear marks, install a new cover gasket and rotate
pump drive shaft by hand to check for smooth
operation.
Inspection
Disassembly/Assembly
Refer to Figure 32 for this procedure.
1. Remove the cover screws, cover and gasket.
Discard the gasket.
NOTE
The pump body and gears are serviced as an
assembly. If one or the other is worn or
damaged, replace the entire pump. No wear
specifications are provided by the manufacturer.
119
GM INLINE ENGINES
32
3
OIL PUMP COMPONENTS
1. Clean all parts thoroughly in solvent. Brush the
inside of the body and the pressure regulator
chamber to remove all dirt and metal particles. Dry
with compressed air, if available.
2. Check the pump body and cover for cracks or
excessive wear.
3. Check the pressure regulator valve for a proper
fit.
4. Check the pump gears for damage or signs of
excessive wear.
5. Check the drive gear shaft-to-body fit for
excessive looseness.
6. Check the inside of the pump cover for wear
that could allow oil to leak around the ends of the
gears.
CYLINDER HEAD
Removal
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Pressure regulator valve
Pressure regulator spring
Retaiding pin
Screws
Pump cover
Cover gasket
Idler gear
Drive gear and shaft
Pump body
Pickup screen and pipe
Perform Steps 1-8 if engine is in boat. If engine
has been removed from boat, begin with Step 9.
1. Remove the intake and exhaust manifolds as
described in this chapter.
2. Open the engine block drain valve(s) and allow
the water to drain.
3. Disconnect the fuel line support clamps.
Remove the fuel line.
4. Disconnect the cooling hoses at the water
distribution housing.
5. Disconnect the temperature sending lead and
remove the water distribution housing.
6. Disconnect and remove ignition coil. (Figure
33).
7. Remove
circuit breaker bracket and engine
lifting eye.
8. Disconnect all spark plug cables. Remove the
spark plugs.
9. Remove the rocker arm cover as described in
this chapter.
10. Loosen the rocker arms and rotate them to one
side. Remove the pushrods and identify each for
reinstallation in their original position.
11. Loosen the cylinder head bolts, working from
the center of the head to the end in each direction.
12. Remove the head bolts. Tap the end of the
head with a plastic hammer to break the gasket
seal. Remove the head from the engine.
CA UTION
Place the head on its side to prevent damage to
the spark plugs or head gasket surface.
13. Remove and discard the head gasket.
I $1;
‘I“
CHAPTER SIX
120
Decarbonizing
1. Without removing the valves, remove all
deposits from the combustion chambers, intake
ports and exhaust ports. Use a fine wire brush
dipped in solvent or make a scraper from
hardwood. Be careful not to scratch or gouge the
combustion chambers.
2. After all carbon is removed from the
combustion chambers and ports, clean the entire
head in solvent.
3. Clean away all carbon on the piston tops. Do
not remove the carbon ridge at the top of the
cylinder bore.
4. Remove the valves as described in this chapter.
5. Clean the pushrod guides, valve guide bores and
all bolt holes. Use a cleaning solent to remove dirt
and grease.
6. Clean the valves with a fine wire brush or
buffing wheel.
Inspection
1. Check the cylinder head for signs of oil or water
leaks before cleaning.
2. Clean the cylinder head thoroughly in solvent.
While cleaning, look for cracks or other visible
signs of damage. Look for corrosion or foreign
material in the oil and water passages (Figure 34).
Clean the passages with a stiff spiral brush, then
blow them out with compressed air.
3. Check the cylinder head studs for damage and
replace, if necessary.
4. Check the threaded rocker arm studs or bolt
holes for damaged threads. Replace if necessary.
5. Check the cylinder head-to-block surface for
warpage with a straightedge and feeler gauge
(Figure 35). Compare to specifications (Table 1 or
Table 2). If gap exceeds specifications, have the
head resurfaced by a dealer or machine shop. If
head resurfacing is required, do not remove more
than 0.010 in. Replace the head if a greater amount
must be removed to correct warpage.
Installation
1. Make sure the cylinder head and block gasket
surfaces and bolt holes are clean. Dirt in the block
bolt holes or on the head bolt threads will affect
tightening torque.
2. Recheck all visible oil and water passages for
cleanliness.
CA UTION
Do not use steel automotive-type gaskets. Use
only MerCap replacement head gaskets in Step
3.
121
GM INLINE ENGINES
035
3. Fit a new MerCap head gasket over the cylinder
dowels on the block (Figure 36).
4. Install the cylinder head to the block. Wipe the
head bolt threads with Perfect Seal (C-92-34227)
and install finger-tight.
5. Tighten head bolts l/2 turn at a time following
the sequence shown in Figure 37 until specified
torque is reached. See Table 3.
CA UTION
Retorque &cylinder head bolts during 20-hour
checkup. This will prevent possible poor engine
performance, a blown head gasket, burned valves
and other engine problems.
6. If engine is in boat, reverse Steps l- 10 of
Removal in this chapter. If engine is out of boat,
reverse Step 9 and Step 10 of Removal to complete
installation.
VALVES AND VALVE SEATS
Some of the following procedures must be done
by a dealer or machine shop, since they require
special knowledge and expensive machine tools.
Others, while possible for the home mechanic, are
difficult or time-consuming. A general practice
among those who do their own service is to remove
the cylinder head, perform all disassembly except
valve removal, then take the head to a machine
shop for inspection and service. Since the cost is
low relative to the required effort and equipment,
this is usually the best approach, even for
experienced mechanics. The following procedures
are given to acquaint the home mechanic with
what the dealer or machine shop will do.
4-cylinder models
&cylinder models
CHAPTER SIX
122
Valve
Removal
Refer to Figure 38 for this procedure.
1. Remove the cylinder head as described in this
chapter.
2. Remove the rocker arm assemblies as described
in this chapter.
3. Compress the valve spring with a compressor
tool like the one shown in Figure 39. Remove the
retainer locks and release the spring tension.
4. Remove the valve spring cap, shield, spring and
damper assembly.
5. Remove the valve stem seal with a pair of
pliers. See Figure 40. Discard the seal.
CA UTION
Remove any burrs from the valve stem lock
grooves before removing the valves or the valve
guides will be damaged.
6. Remove the valve and repeat Steps 3-5 on each
remaining valve.
7. Arrange the parts in order so they can be
returned to their original positions w h e n
reassembled.
Inspection
1. Clean the valves with a fine wire brush or
buffing wheel. Discard any cracked, warped or
burned valves.
2. Measure valve stems at the top, center and
bottom for wear. A machine shop can do this when
the valves are ground. Also measure the length of
each valve and the diameter of each valve head.
NOTE
Check the thickness of the valve edge or margin
after the valves have been ground. See Figure 41.
Any valve with a margin of less than l/32 in.
should be discarded.
3. Remove all carbon and varnish from the valve
guides with a stiff spiral wire brush.
NOTE
The next step assumes that all valve stems have
been measured and are within specifications.
Replace valves with worn stems before
performing this step.
4. Insert each valve into the guide from which it
was removed. Holding the valve just slightly off its
seat, rock it back and forth in a direction parallel
123
GM INLINE ENGINES
with the rocker arms. This is the direction in which
the greatest wear normally occurs. If the valve stem
rocks more than slightly, the valve guide is
probably worn.
5. If there is any doubt about valve guide
condition after performing Step 4, have the valve
guide measured with a valve stem clearance
checking tool. Compare the results to specifications
(Table 1 or Table 2) according to engine. Worn
guides must be reamed for the next oversize valve
stem.
6. Test the valve springs under load on a spring
tester (Figure 42). Replace any weak springs.
7. Check each spring on a flat surface with a steel
square. See Figure 43. Slowly revolve spring 360
and note the space between the top of the coil and
the square. If it exceeds 5/16 in. at any point,
replace the spring.
8. Inspect the valve seat inserts. If worn or burned,
they must be reconditioned. This is a job for a
dealer or machine shop, although the procedure is
described in this chapter.
Valve Guide Reaming
Worn valve guides must be reamed to accept a
valve with an oversize stem. Reaming must be
done by hand (Figure 44) and is a job best left to an
experienced machine shop. The valve seat must be
refaced after the guide has been reamed.
Valve Seat Reconditioning
1. Cut the valve seats to the specified angle (Table
1 or Table 2) with a dressing stone. Remove only
enough metal to obtain a good finish.
6
CHAPTER SIX
124
2. Use tapered stones to obtain the specified seat
width when necessary.
3. Coat the corresponding valve face with Prussian
blue dye.
4. Insert the valve into the valve guide.
5. Apply light pressure to the valve and rotate it
approximately l/4 turn.
6. Lift the valve out. If it seats properly, the dye
will transfer evenly to the valve face.
7. If the dye transfers to the top of the valve face,
lower the seat. If it transfers to the bottom of the
valve face, raise the seat.
Valve
045
Installation
NOTE
Install all parts in the same positions from which
they were removed.
1. Coat the valves with oil and install them in the
cylinder head.
2. Install new oil seals on each valve with a deep
socket and hammer.
3. Drop the valve spring shim around the valve
guide boss. Install the valve spring over the valve,
then install the spring retainer.
4. Compress the spring and install the locks. Make
sure both locks seat properly in the upper groove of
the valve stem.
5. Measure the installed spring height between the
top of the valve seat and the underside of the
spring retainer. See Figure 45. If height is greater
than specifications, install an extra spring seat shim
about l/16 in. thick and remeasure the height.
Valve
Adjustment
Stem-to-rocker arm clearance must be within
specifications when the hydraulic lifter is
completely collapsed. If valve clearance is not
sufficient, the valve opens early and closes late,
resulting in a rough engine idle. Excessive clearance
lets the valve open too soon and close too early,
causing valve bounce and damage to the camshaft
lobe.
Valve adjustment is only required when the
cylinder head valve train has been disassembled.
Adjust the valves with the lifter on the base circle
of the camshaft lobe.
1. Rotate the crankshaft until the pulley notch
aligns with the zero mark on the timing tab. This
positions the No. 1 cylinder at TDC. This position
can be verified by placing a finger on the No. 1
046
GM INLINE ENGINES
0
47
048
125
rocker arms as the pulley notch nears the zero
mark. If the valves are moving, the engine is in the
No. 4 (bcylinder) or No. 6 (6-cylinder) firing
position. Rotate the crankshaft pulley one full turn
to reach the No. 1 firing position.
2. With the engine in the No. 1 firing position,
refer to Figure 46 and adjust the following valves:
a. No. 1 exhaust and intake.
b. No. 2 intake.
c. No. 3 exhaust.
d. No. 4 intake.
e. No. 5 exhaust (6-cylinder only).
3. Back off the adjusting nut until lash is felt at the
pushrod, then turn the nut in to remove all lash.
When lash has been removed, the pushrod will not
rotate. Turn the nut in an additional 3/4 turn to
center the lifter plunger. See Figure 47.
4. Rotate the crankshaft one full turn to realign the
pulley notch and the timing tab zero mark in the
No. 4 (4-cylinder) or No. 6 (6-cylinder) firing
position. Refer to Figure 46 and adjust the
following valves:
a. No. 2 exhaust.
b. No. 3 intake.
c. No. 4 exhaust.
d. No. 5 intake (6-cylinder only).
e. No. 6 intake and exhaust (6-cylinder only).
PISTON/CONNECTING
ASSEMBLY
ROD
Piston Removal
1. Remove the engine as described in this chapter.
2. Place a 6-quart container under the oil pan and
remove the drain plug. Let the crankcase oil drain.
3. Remove the exhaust manifold as described in
this chapter.
4. Remove the cylinder head as described in this
chapter.
5. Remove the oil pan and oil pump as described
in this chapter.
6. Pack the cylinder bore with clean shop rags.
Remove the carbon ridge at the top of the cylinder
bore with a ridge reamer. These can be rented for
use. Vacuum out the shavings, then remove the
shop rags. Repeat this step for each cylinder.
7. Rotate the crankshaft so the connecting rod is
centered in the cylinder bore.
8. Measure the clearance between each connecting
rod and the crankshaft journal flange with a feeler
gauge (Figure 48). If the clearance exceeds
specifications (Table 1 or Table 2) replace the
connecting rod.
126
CHAPTER SIX
GM INLINE ENGINES
127
9. Remove the nuts holding the connecting rod
cap. Lift off the cap, together with the lower bearing
insert (Figure 49).
NOTE
the connecting rod caps are dijicult to remove,
tap the studs with a wooden hammer hatdle
If
(Figure 50).
10. Use the wooden hammer handle to push the
piston and connecting rod from the bore.
NOTE
Mark the cylinder number on the top of each
piston with quick-drying paint. Check for
cylinder numbers or identification marks on the
connecting rod and cap. If they are not visible,
make your own (Figure 51).
n
w52
11. Remove the piston rings with a ring remover
(Figure 52).
Piston
Pin
Removal/Installation
The piston pins are press-fitted to the connecting
rods and hand-fitted to the pistons. Removal
requires the use of a press and support stand. This
is a job for a dealer or machine shop equipped to fit
the pistons to the pin, ream the pin bushings to the
correct diameter and install the pistons and pins on
the connecting rods.
Piston Clearance Check
Unless you have precision measuring equipment
and know how to use it properly, have this
procedure done by a machine shop.
1. Measure the piston diameter with a micrometer
(Figure 53). Measure just below the rings at right
angles to the piston pin bore.
2. Measure the cylinder bore diameter with a bore
gauge (Figure 54). Measure at the top, center and
bottom of the bore, in front-to-rear and
side-to-side directions.
3. Subtract the piston diameter from the largest
cylinder bore reading. If the difference exceeds
specifications (Table 1 or Table 2), the cylinder
must be rebored and oversized pistons installed.
Piston
Ring
Fit/Installation
1. Check the ring gap of each piston ring. To do
this, position the ring at the bottom of the ring
Q
CHAPTER SIX
128
travel area and square it by tapping gently with an
inverted piston. See Figure 55.
055
NOTE
If the cylinders have not been rebored, check the
gap at the bottom of the ring travel, where the
cylinder is least worn.
.
2. Measure the ring gap with a feeler gauge as
shown in Figure 56. Compare with specifications.
If the measurement is not within specifications
(Table 1 or Table 2), replace the rings as a set.
3. Check the side clearance of the compression
rings as shown in Figure 57. Place the feeler gauge
alongside the ring all the way into the groove. If the
measurement is not within specifications (Table 1
or Table 2) either the rings or ring grooves are
worn. Inspect and replace as necessary.
4. Using a ring expander tool (Figure 58), carefully
install the oil control ring, then the compression
rings.
NOTE
Oil rings consist of 3 segments. The wavy
segment goes between the flat segments to act as
a spacer. Upper and lower flat segments are
056
GM INLINE ENGINES
129
interchangeable.
The top sides of both
compression rings are marked with a symbol.
The marked side of the ring must face the top qf
the piston.
5. Position the ring gaps as shown in Figure 59.
Connecting Rod Inspection
Have the connecting rods checked for
straightness by a dealer or machine shop.
Connecting rods can spring out of alignment during
shipping or handling. When installing new
connecting rods, have them checked for
misalignment before installing the piston and
piston pin.
Connecting Rod Bearing
Clearance Measurement
1. Place the connecting rods and upper bearing
halves on the proper connecting rod journals.
2. Cut a piece of Plastigage the width of the
bearing (Figure 60). Place the Plastigage on the
journal, then install the lower bearing half and cap.
NOTE
Do not place Plastigage over the journal oil
hole.
3. Tighten the connecting rod cap to specifications
(Table 3). Do not rotate the crankshaft while the
Plastigage is in place.
4. Remove the connecting rod cap. Bearing
clearance is determined by comparing the width of
060
0
59
tigage
INLINE-ALL
CYLINDERS
A. Oil ring spacer gear
(tang in hole or slot within arc)
B. Oil ring rail gaps
C. 2nd compression ring gap
D. Top compression ring gap
6
CHAPTER SIX
130
the flattened Plastigage to the markings on the
envelope. See Figure 61. If the clearance is
excessive, the crankshaft must be reground and
undersize bearings installed.
061
Installing
Piston/Connecting
Rod Assemblies
The No. 2 connecting rod on early 181 cid
engines has a ground recess on the camshaft side to
provide clearance for the camshaft fuel pump lobe.
For this reason, the No. 2 rod on these engines
must be reinstalled in its correct cylinder. If this
connecting rod is replaced, the camshaft must also
be replaced, as replacement rods are not ground for
proper clearance and replacement cams have a
smaller fuel pump lobe.
1. Make sure the pistons are correctly installed on
the connecting rods. The small rod bearing tang
should be on the same side as the arrow or notch in
the piston head. See Figure 62.
2. Make sure the ring gaps are positioned as shown
in Figure 59.
Connecting rod
ing rod bearing tan
, 250 and 292 cid
bearing tangs
131
GM INLINE ENGINES
3. Slip short pieces of hose over the connecting rod
studs to keep them from nicking the crankshaft.
Tape will work if you do not have the right
diameter hose, but it is more difficult to remove.
4. Immerse the entire piston in clean engine oil.
Coat the cylinder wall with oil.
5. Install the piston/connecting rod assembly in its
cylinder as shown in Figure 63. Make sure the
number painted on the top of the piston before
removal corresponds to the cylinder number.
NOTE
The notch on the piston must face thefront of the
engine (Figure 64).
6. Clean the connecting rod bearings carefully,
including the back sides. Coat the journals and
bearings with clean engine oil. Place the bearings in
the connecting rod and cap.
7. Remove the protective hose or tape and install
the connecting rod cap (Figure 65). Make sure the
rod and cap marks align. Tighten the cap nuts to
specifications (Table 3).
8. Check the connecting rod big-end play as
described under Piston Removal.
CRANKSHAFT
End Play Measurement
1. Pry the crankshaft to the front of the engine
with a large screwdriver.
2. Measure the crankshaft end play between the
front of the rear main bearing and the crankshaft
thrust surface with a feeler gauge. See Figure 66.
Compare to specifications (Table 1 or Table 2).
6
CHAPTER SIX
132
3. If end play is excessive, replace the rear main
bearing. If less than specified, check the bearing
faces for imperfections.
Removal
1. Remove the engine as described in this chapter.
2. Remove the flywheel as described in this
chapter.
3. Mount the engine on an engine stand, if
available.
4. Remove the starter.
5. Invert the engine to bring the oil pan to an
upright position.
6. Remove the oil pan and oil pump as described
in this chapter.
7. Remove the timing gear cover as described in
this chapter.
8. Remove the spark plugs to permit easy rotation
of the crankshaft.
9. Rotate the crankshaft to position one
connecting rod at the bottom of its stroke.
10. Remove the connecting rod bearing cap and
bearing (Figure 65). Move the piston/rod assembly
away from the crankshaft.
11. Repeat Step 9 and Step 10 for each piston/rod
assembly.
12. Unbolt and remove the main bearing caps with
bearing inserts (Figure 67).
NOTE
If the caps are d@cult to remove, lift the bolts
partway out, then pry the caps from side to side.
NOTE
If you do not have precision measuring
equipment and know how to use it, have a
machine shop perform Step 3.
3. Check all journals and crankpins against
specifications for out-of-roundness and taper. If
necessary, have the crankshaft reground and install
new undersize bearings.
Main Bearing Clearance Measurement
Main bearing clearance is measured with
Plastigage in the same manner as connecting rod
bearing clearance, described in this chapter.
Excessive clearance requires that the bearings be
replaced, the crankshaft be reground or both.
Installation
13. Check the caps for identification numbers or
marks. If none are visible, clean the caps with a
wire brush. If marks still cannot be seen, make
your own with quick-drying paint.
14. Carefully lift the crankshaft from the engine
block. Lay the crankshaft, main bearings and
bearing caps in order on a clean workbench.
15. Remove the main bearing oil seal from the
cylinder block and rear bearing cap.
Inspection
1. Clean the crankshaft thoroughly with solvent.
Blow out the oil passages with compressed air.
2. Check the main and connecting rod journals for
scratches, grooves, scoring or cracks. Check oil seal
surface for burrs, nicks or other sharp edges which
might damage a seal during installation.
1. Install a new rear main bearing oil seal in the
cylinder block and bearing cap grooves. Seal lip
should face front of engine.
2. Lubricate seal lip with clean engine oil. Make
sure oil is kept away from the parting line surface.
3. Install the main bearing inserts in the bores with
their tangs engaging the slots provided in the block.
4. Install the main bearing inserts in the bearing
caps.
5. Carefully lower the crankshaft into position in
the block.
6. Install main bearing caps with their arrows
pointing toward the front of the engine. See Figure
68.
7. Tighten all bearing caps except the rear main to
lo- 12 ft.-lb. Tighten rear main cap to specifications
(Table 3). Tap front of crankshaft with a hammer
133
GM INLINE ENGINES
6. Fit drive coupling on studs. Install washers and
locknuts. Tighten nuts to specifications.
7. Install bell housing.
Inspection
1. Visually check the flywheel surfaces for cracks,
deep scoring, excessive wear, heat discoloration
and checking.
2. Have the face runout checked with a dial
indicator and compare to specifications.
3. Check surface flatness with a straightedge and
feeler gauge.
4. Inspect the ring gear teeth for cracks, broken
teeth or excessive wear. If severely worn, check the
starter motor drive teeth for similar wear or
damage. Replace as indicated.
5. Lubricate engine coupling splines with
Multipurpose Lubricant (part No. C-92-63250). If
boat is used mainly for trolling, use Universal Joint
Lubricant (part No. C-92-74057Al) for better
results.
CYLINDER BLOCK
Cleaning and Inspection
to drive it rearward, then tap the rear to drive it
forward. This aligns the rear main bearing and
crankshaft thrust surfaces.
8. Retighten all main bearing caps to specifications
(Table 3).
9. Measure crankshaft end play as described in this
chapter.
10. Reverse Steps I- 10 of Removal in this chapter.
FLYWHEEL
Removal/Installation
1. Remove the engine as described in this chapter.
2. Remove the bell housing.
3. Remove the coupler retaining nuts and washers.
Remove the coupler.
4. Unbolt and remove the flywheel.
5. To install, align dowel hole in flywheel with
dowel hole in crankshaft flange and position
flywheel on studs.
1. Clean the block thoroughly with solvent.
Remove any gasket residue from the machined
surfaces. Check all core plugs for leaks and replace
any that are suspect. See Cove Plugs in this chapter.
Remove any plugs that seal oil passages. Check oil
and coolant passages for sludge, dirt and corrosion
while cleaning. If the passages are very dirty, have
the block boiled out by a machine shop. Blow out
all passages with compressed air. Check the threads
in the head bolt holes to be sure they are clean. If
dirty, use a tap to true up the threads and remove
any deposits.
2. Examine the block for cracks. To confirm
suspicions about possible leak areas, use a mixture
of one part kerosene and 3 parts engine oil. Coat
the suspected area with this solution, then wipe dry
and immediately apply a solution of zinc oxide
dissolved in wood alcohol. If any discoloration
appears in the treated area, the block is cracked and
should be replaced.
3. Check flatness of the cylinder block deck. Place
an accurate straightedge on the block. If there is
any gap between the block and straightedge,
measure it with a feeler gauge. Measure from end
to end and from corner to corner, as shown in
Figure 69. Have block resurfaced if out of
specifications.
6
CHAPTER SIX
134
4. Measure the cylinder bores with a bore gauge
(Figure 70) as described in Step 2, Piston Clearance
Check in this chapter. If the cylinders exceed
maximum tolerances, they must be rebored.
Reboring is also necessary if the cylinder walls are
badly scuffed or scored. Before boring, install all
main bearing caps and tighten the cap bolts to
specifications in Table 3.
CORE PLUGS
Check the condition of all core plugs in the block
(Figure 71) and cylinder head whenever the engine
is out of the boat for service. If any signs of leakage
or corrosion are found around one plug, replace
them all.
Removal/Installation
Do not
will be
restrict
engine
CA UTION
drive core plugs into the engine casting. It
impossible to retrieve them and the.v can
coolant circulation, resulting in serious
damage.
1. Tap the bottom edge of the core plug with a
hammer and drift. Use several sharp blows to push
the bottom of the plug inward, tilting the top out
(Figure 72).
2 . Grip the top of the plug with pliers. Pull the plug
from its bore (Figure 73) and discard.
3. Clean the plug bore thoroughly to remove all
traces of the old sealer.
4. Apply a light coat of Loctite Stud N’ Bearing
mount or equivalent to the plug bore.
5. Install the new core plug with an appropriate
size driver or socket. The sharp edge of the plug
should be at least 0.02 in. inside the lead-in
chamfer.
gauge
GM INLINE ENGINES
135
Strike here with hammer
Remove plug
L&f
n
Table 1 4GYLINDER
Type
Displacement
Model 110 and 120
Model 140
Bore
153 cid
181 cid
Stroke
153 cid
181 cid
Cylinder numbering (front to rear)
Firing order
Cylinder bore
Out-of-round
Taper
Head-to-block surface
Piston clearance
Piston rings
Groove clearance
Top compression
2nd compression
Oil
Gap
Top compression
2nd compression
Oil
Piston pin
Diameter
Clearance
Fit in rod
ENGINE SPECIFICATIONS
Mine 4-cylinder
153 cid
181 cid
3.875 in.
4.000 in.
3.25 in.
3.80 in.
l-2-3-4
l-3-4-2
0.0005 in. max.
0.0005 in. max.
0.005 in. per 8 ins.
0.0005-0.0015 in.
0.0012-0.0027 in.
0.0012-0.0032 in.
0.000-0.005 in.
0.010-0.020 in.
0.010-0.030 in.
0.015-0.055 in.
0.9270-0.9273 in.
0.00015-0.00025 in.
0.0008-0.0016 interference
(continued)
CI-IAPTER SIX
136
Table
1 4-CYLINDER
Crankshaft
Main journal diameter
Main journal taper
Main journal out-of-round
Main bearing clearance
End play
Crankpin diameter
153 cid
181 cid
Crankpin taper
Crankpin
out-of-round
Connecting rod
Bearing clearance
153 Ad
181 cid
Side clearance
153 cid
181 cid
Camshaft
Lobe lift
Model 110 (153 cid)
Model 120 (153 cid)
Model 140 (181 cid)
Journal diameter
Runout
Valves
Lifter
Rocker arm ratio
Lash
Face angle
Seat angle
Seat runout
Seat width
Intake
Exhaust
Stem clearance
Intake
Exhaust
Valve springs
Free length
153 cid
181 cid
Pressure
153 cid
Closed
Open
181 cid
Closed
Open
Installed height (-t l/32 in.)
Damper free length 153 cid
ENGINE SPECIFICATIONS (continued)
2.2983-2.2993 in.
0.0002 in. max.
0.0002 in. max.
0.0003-0.0029 in.
0.002-0.008 in. max.
1.999-2.000
2.099-2.100
0.0003 in.
0.0002 in.
in.
in.
max.
max.
0.0007-0.0027
0.0007-0.0028
in.
in.
0.0085-0.0135 in.
0.009-0.013 in.
0.1914 in.
0.2325 in.
0.2525 in.
1.8882-I .8892 in.
0.0015 in. max.
Hydraulic
1.7&l
3/4 turn down from zero lash
45"
46"
0.002 in. max.
l/32-1/16 in.
t/16-3/32 in.
0.0010-0.0027 in.
0.0015-0.0032 in.
2.08 in.
Not specified
78-88 lb. Q 1.86 in.
170-180 lb. Q 1.26 in.
83 lb. Q 1.66 in.
175 lb. Q 1.26 in.
1.8562 in.
1.94 in.
I
GM INLINE
137
ENGINES
Table 2 O-CYLINDCR
Displacement
Model 140
Model 150
Model 160 and 165
Model 200
Bore
194 cid
230 cid
250 cid
292 cid
Stroke
194 cid
230 cid
250 cid
292 cid
Cylinder numbering (front to rear)
Firing order
Cylinder bore
Out-of-round
Taper
Head-to-block surface
Piston clearance
194 cid
230,250 cid
292 cid
Piston rings
Groove clearance
Except 292 cid
Top compression
2nd compression
Oil
292 cid
Top compression
2nd compression
Oil
Gap
Top compression
2nd compression
Oil
Piston pin
Diameter
Clearance
Except 292 cid
292 cid
Fit in rod
ENOINE 6PWIFICAWDN6
194
230
250
292
cid
cid
cid
cid
3.56 in.
3.675 in.
3.675 in.
3.875 in.
3.25 in.
3.25 in.
3.53 in.
4.12 in.
l-2-3-4-5-6
l-5-3-6-2-4
0.0005 in. max.
0.0005 in. max.
0.005 in. per 6 ins.
0.0006-0.0010 in.
0.0005-0.0015 in.
0.0026-0.0032 in.
O.W12-0.0027 in.
0.0012-0.0032 in.
O.OOO-0.005 in.
O.W20-0.0040 in.
O.W20-0.0040 in.
0.0005-0.0055 in.
0.010-0.020 in.
0.010-0.030 in.
0.015-0.055 in.
0.9270-0.9273 in.
0.0015-O.OW25 in.
0.025-0.00035 in.
O.W06-0.0016 interference
(continued)
CHAPTER SIX
138
Table
Crankshaft
Main journal diameter
Main journal taper
Main journal out-of-round
Main bearing clearance
194 cid
230, 250 cid
292 cid
End play
Crankpin diameter
Crankpin taper
Crankpin out-of-round
2
&CYLINDER
ENDINE
SPECIFICATIONS
2.2993-2.2993 in.
0.0002 in. max.
0.0002 in. max.
.
0.0009-0.0034 in.
0.0003-0.0029 in.
0.0009-0.0034 in.
0.002-0.006 in. max.
1.999-2.000 in.
0.0093 in. max.
0.0002 in. max.
Connecting rod
Bearing clearance
194, 230, 250 cid
292 cid
Side clearance
194 cid
230, 250, 292 cid
0.0007-0.0027
0.0007-0.0028
0.0085-0.0135
0.0008-0.0014
0.0085-0.0135
Camshaft
Lobe lift
194, 230 cid
250 cid
292 cid
Journal diameter
Runout
0.1914 in.
0.2297 In.
0.2525 in.
1.8682-l .8692 in.
0.0015 in. max.
Valves
Lifter
Rocker arm ratio
Lash
Face angle
Intake
Exhaust
194, 230, 250 cid
292 cid
Seat angle
Seat runout
Seat width
Intake
194, 292 cid
230, 250 cid
Exhaust
Stem clearance
Intake
Exhaust
(continued)
in.
in.
in.
in.
in.
Hydraulic
1.75:1
314 turn down from zero lash
45”
45”
46”
46”
0.002 in. max.
l/32-1/16 in.
l/32-3/32 in.
l/16-3/32 in.
0.0010-0.0027 in.
0.0015-0.0032 in.
(continued)
139
GM INLINE ENGINES
Table 2 6-CYLINDER
Valve springs
Free length
194 cid
230, 250, 292 cid
Pressure
194 cid
Closed
Open
230 cid
Closed
Open
250 cid
Closed
Open
292 cid
Closed
Open
Installed height ( f l/32 in.)
Except 292 cid exhaust
292 cid exhaust
Damper free length
292 cid
ENGINE SPECIFICATIONS (continued)
2.03 in.
1.90 in.
84-92 lb. Q 1.88 in.
183-173 lb. @ 1.33 in.
54-84 lb. Q 1.80 in.
170-184 lb. Q 1.33 in.
54-84 lb. @ 1.88 in.
180-192 lb. @ 1.27 in.
85-93 lb. Q 1.89 in.
174-184 lb. Q 1.30 in.
1.8582 in.
1.825 in.
1.94 in.
Table 3 TIGHTENING TORQUES
Fastener
&lb.
Camshaft thrust plate
Carburetor flange bolts
Connecting rod cap nuts
11132-24
318-24
Crankshaft pulley
Coupling-to-flywheel
1987
All others
Cylinder head bolts
Distributor clamp
Flywheel
housing-to-block
Front mount-to-block
Main bearing cap
Manifold-to-head
Oil pan
Side screws
End screws
Drain plug
Oil pump
Cover
To block
Pickup
Rocker arm cover
Spark plugs
With gasket
Without gasket
Timing gear cover
Water
pump-to-block
8
12
33
40
18
80
35
93
20
21
21
85
23
7
10
23
8
10
5
4
25
15
8
15
6
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