Mercury BRAVO Service Manual page 38

TROUBLESHOOTING
Drive Shaft Housing Noise (Continued)
Boat transom too thin. Thickness: 2
in. (51mm) minimum, 2-1/4 in. (57mm)
maximum.
Boat transom thickness uneven. This
could affect engine to transom
assembly alignment and is usually not
detectable with alignment tool.
Variation: 1/8 in. (3mm) maximum.
Bell housing contacting gimbal ring.
This would cause knocking in the fully
trimmed IN position only.
Stringer height uneven or transom
assembly installed cocked on boat
transom. This will affect engine
alignment, but is usually not detectable
with alignment tool.
Weak boat transom or boat bottom
that flexes under power and causes
engine misalignment - this condition
will usually cause engine coupler
failure.
Rear engine mount attaching
hardware improperly installed or
missing.
Engine mounting holes drilled
off-center in inner transom plate
engine supports or engine flywheel
housing
Misalignment between bell housing,
gimbal housing and engine coupler.
Page 1C-6
Cause
SERVICE MANUAL NUMBER 28
Special Instructions
Add thickness to transom.
Repair boat as necessary.
Check for soft or split trim cylinder
bushings and loose or worn hinge pin
bushings. (Refer to SECTION 5B)
Measure the distance between the
engine flywheel housing and the inner
transom plate on both sides. If
distances are uneven, the problem
may be due to uneven stringer height
or a cocked transom assembly. Adjust
the stringer height or relocate the
transom cutout as required.
This condition can sometimes be
detected by having someone apply
force to the top of the drive unit while
watching the inner transom plate. If
movement can be observed, the
transom is weak and must be repaired.
Reinstall hardware correctly.
Make sure the holes are equally
spaced fore and aft and are equal
distance from the centerline.
Contact your service center and
arrange to have a technical service
representative check the unit using a
special gauge.
90-863160 MAY 2000