2001 Mercury Mariner 50-60HP Factory Service Manual, Page 48Get this manual
GENERAL INFORMATION
4Increase steering torque or pull to the left at normal installation height (with the normal right hand rotation propeller)5In excess, cause boat "porpoising" (bouncing) or propeller ventilation6Cause engine overheating if any water intake holes are above the water line
Trim "In" Angle Adjustment
Some outboard boats, particularly some bass boats, are built with greater than normal transom angle which will allow the outboard to be trimmed further "in" or "under"This greater trim "under" capability is desirable to improve acceleration, reduce the angle and time spent in bow high boat, altitude during planing off, and in some cases, may be necessary to plane off boat with aft live wells, given the variety of available propellers and height range of engine installationsHowever, once on plane, the engine should be trimmed to more intermediate position to avoid bow-down planing condition called "plowing"Plowing can cause "bow steering" or "over steering" and inefficiently consumes horsepowerIn this condition, if attempting turn or encountering diagonal, moderate wake, more abrupt turn than intended may resultIn rare circumstances, the owner may decide to limit the trim inThis can be accomplished by repositioning the tilt stop pins into whatever adjustment holes in the transom brackets is desired