Performance Troubleshooting; Low Wot Engine Rpm; High Wot Engine Rpm; Propeller Ventilating/Cavitating - Mercury BRAVO Service Manual

TROUBLESHOOTING

Performance Troubleshooting

Low WOT Engine RPM

Improper drive unit trim angle.
Damaged propeller.
Improper propeller pitch.
Dirty or damaged boat bottom.
Drive installation too low on transom.
Permanent "hook" in boat bottom
(some boats are built with a slight
"hook" for correct boat performance).
"Power hook" or weak boat bottom.

High WOT Engine RPM

Propeller ventilating.
Improper propeller pitch.
Propeller hub slipping.
Drive installation too high on transom.
Engine coupler hub spun.

Propeller Ventilating/Cavitating

Drive unit trimmed too high.
Incorrect propeller.
Page 1C-8
Cause
Cause
Cause
SERVICE MANUAL NUMBER 28
Special Instructions
Properly adjust drive unit trim angle.
Repair or replace.
Water test boat using a lower pitch
propeller.
Clean and/or resurface boat bottom.
Contact boat manufacturer for
installation specifications.
Check for a hook in the boat bottom
by placing a straight edge, at least 6 ft.
(2m) long, under the bottom edge of
the transom. If a hook is found,
contact the boat manufacturer.
Water test boat. Boat will perform
normally until hook develops at
high speed, then loss of rpm and
speed will occur. Contact boat
manufacturer.
Special Instructions
Determine cause for ventilation.
Water test boat using a higher pitch
propeller.
Replace hub or replace propeller.
Contact boat manufacturer for
installation specifications.
Replace coupler.
Special Instructions
Trim drive unit IN/DOWN.
Install correct propeller.
90-863160 MAY 2000