Placing Tilt Pin In Upper Holes; Trim Tab Adjustment - Mercury/Mariner 25 MARATHON Service Manual

OUTBOARD MOTOR INSTALLATION

Placing Tilt Pin in Upper Holes

1. Lift the bow out of the water.
2. Generally increase top speed.
3. Increase clearance over submerged objects or a shallow bottom.
4. Increase steering torque or pull to the left at a normal installation height (with the nor-
mal right hand rotation propeller).
5. In excess, cause boat " porpoising"(bouncing) or propeller ventilation.

Trim Tab Adjustment

Propeller steering torque may cause boat to pull in one direction. This steering torque re-
sults from outboard not being adjusted so the propeller shaft is parallel to the water sur-
face. The trim tab can help compensate for this steering torque and can be adjusted within
limits to reduce any unequal steering effort.
NOTE: Trim tab adjustment will have little effect reducing steering torque if the outboard
is installed with the anti-ventilation plate approximately 2 inches (50mm) or more above
the boat bottom.
Operate boat at normal cruising speed, with the outboard set at the desired transom angle
adjustment. Turn boat left and right and note the direction the boat turns more easily.
If adjustment is necessary, loosen trim tab bolt and make small adjustments at a time. If
the boat turns more easily to the left, move the trailing edge of trim tab to the left. If the
boat turns more easily to the right move the trailing edge of trim tab to the right. Retighten
bolt and retest.
Page 1D-12 90-826883R2 JUNE 1998