TOHATSU 2.5 Owner's Manual page 15

* Correct angle of trim
The optimum angle of trim is obtained when the boat is parallel to the water
surface while running.
* Incorrect angle of trim (bow rises too high)
If the angle of trim is excessive. the bow will rise out of the water and the
speed will decrease. In this case, decrease the angle by setting the thrust rod
in a lower hole.
* Incorrect angle of trim (bow dips into the water)
If the trim angle is too small, the bow will dip into water, the speed will
decrease, and water may enter the boat.
In this case, increase the angle by setting the thrust rod in a higher hole.