TROUBLESHOOTING SERVICE MANUAL NUMBER 28
Page 1C-8 90-863160 MAY 2000
Performance Troubleshooting
Low WOT Engine RPM
Cause Special Instructions
Improper drive unit trim angle. Properly adjust drive unit trim angle.
Damaged propeller. Repair or replace.
Improper propeller pitch.
Water test boat using a lower pitch
propeller.
Dirty or damaged boat bottom. Clean and/or resurface boat bottom.
Drive installation too low on transom.
Contact boat manufacturer for
installation specifications.
Permanent “hook” in boat bottom
(some boats are built with a slight
“hook” for correct boat performance).
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.
“Power hook” or weak boat bottom.
Water test boat. Boat will perform
normally until hook develops at
high speed, then loss of rpm and
speed will occur. Contact boat
manufacturer.
High WOT Engine RPM
Cause Special Instructions
Propeller ventilating. Determine cause for ventilation.
Improper propeller pitch.
Water test boat using a higher pitch
propeller.
Propeller hub slipping. Replace hub or replace propeller.
Drive installation too high on transom.
Contact boat manufacturer for
installation specifications.
Engine coupler hub spun. Replace coupler.
Propeller Ventilating/Cavitating
Cause Special Instructions
Drive unit trimmed too high. Trim drive unit IN/DOWN.
Incorrect propeller. Install correct propeller.
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