ENGINE
Inspecting the Cylinder Block and Components
12/05
6LY3 Service Manual
5-53
© 2007 Yanmar Marine International
Inspecting the Flywheel and Housing
The function of the flywheel
(Figure 5-75, (1))
is to
dampen the fluctuating torque loads delivered by
the crankshaft and deliver smooth crankshaft
rotation. It does so by resisting intermittent
rotational force during the power stroke and
provides inertial momentum during the non-power
strokes. The flywheel is secured to the crankshaft
at the end opposite the drive shaft housing with six
bolts. It is covered by the flywheel housing which is
bolted to the cylinder block.
The damper disc is installed on the crankshaft side
of the flywheel. The rotation of the crankshaft is
transmitted through this disc to the input shaft of
the reduction and reversing gear. The reduction
and reversing gear is installed to the flywheel
housing.
The flywheel is balanced by holes drilled in its
circumference.
The ring gear
(Figure 5-75, (4))
is shrink fit to the
circumference of the flywheel. The ring gear serves
to start the engine by meshing with the starter
motor pinion.
The stamped letter and line, which show top dead
center of each cylinder, are positioned on the
flywheel circumference. By matching these marks
with the arrow mark at the hole of the flywheel
housing, the rotary position of the crankshaft can
be ascertained in order to adjust tappet clearance
or fuel injection timing.
Replacing the Ring Gear
• Heat the ring gear evenly at its circumference.
• Use a copper bar
(Figure 5-75, (2))
or other soft
metal and carefully tap the ring gear off the
flywheel evenly around the whole circumference.
Figure 5-75
Figure 5-75
1 – Flywheel
2 – Copper Bar
3 – Wooden Stand
4 – Ring Gear
Positioning Top Dead Center
The top dead center is set by matching index marks
(Figure 5-76, (2))
on the flywheel in the hole of
flywheel housing
(Figure 5-76, (1))
.
Figure 5-76
Figure 5-76
1 – Flywheel Housing
2 – Matching Index Marks
Flywheel Specifications
Outside Diameter of the Flywheel
392 mm
(15.433 in.)
Width of the Flywheel
73.9 mm
(2.909 in.)
GD
2
Value
2.95 kgf·m
2
(21.337 lb-ft)
Fixing Part of
the Crankshaft
Pitch Circle Diameter
of the Bolts
70 mm
(2.755 in.)
No. of Thread Holes
6-Ø16.5 mm
(0.6496 in.)
Fit Joint Diameter
95 mm
(+0.035, 0)
(3.7401 in.)
Ring Gear
Center Diameter
387 mm
(15.2361 in.)
No. of Teeth
129
Shrink Range of the Ring Gear
0.21-0.45 mm
(0.0082-0.0177 in.)
0005661
(2)
(
3
)
(4)
(1)
0005662
(2)
(1)
