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POWERHEAD
TEST PROCEDURES
TEST PROCEDURES
Compression
Testing
Start and run outboard until it achieves operating
temperature, then shut
OFF.
Remove lower side covers. Refer to SIDE COVER
on
p.
180.
Remove spark plugs
Advance throttle linkage to
WOT.
Install compression tester's hose attachment into
spark
plug hole.
004475
132
ill
WARNING
ill
Disconnect
the
safety lanyard
from
the
emergency
stop
switch
prior
to
cranking
the engine.
This
will
prevent
any
residual
fuel
from
the
cylinders
from
being
ignited
by
a
spark
from
the
spark
plug
cap.
While cranking outboard with starter, note maxi-
mum pressure reading
on
gauge. Repeat proce-
dure for each
cylinder.
IMPORTANT: The values shown are guidelines
only,
not absolute service limits.
Cylinder
Compression
Test
Standard
78 to
120 psi
(models with decom-
(550 to 850 kPa)
pression system)
Standard
116
to 175
psi
(models without decom-
(820 to 1230 kPa)
pression system)
Maximum difference
14
psi (100 kPa)
between cylinders
If
engine shows a variation greater than
14
psi
(100 kPa) between cylinders, check for:
• Excessively worn cylinder wall
•
Worn piston
• Worn or stuck piston rings
• Poor seating
of
valves
• Ruptured or damaged cylinder head gasket
Install all parts that were removed.
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