Mercury 300 XS OptiMax Manual page 144

However, once on plane, the engine should be trimmed to a more intermediate
position to avoid a bow‑down planing condition called plowing. Plowing can
cause bow steering or oversteering and inefficiently consumes horsepower.
Stainless Steel Tilt Pin
The owner may decide to limit the trim in. This can be accomplished by
purchasing a stainless steel tilt pin from your dealer and insert it in whatever
adjustment hole in the transom brackets is desired. A nonstainless steel
shipping bolt should not be used in this application other than on a temporary
basis.
OUTBOARD INSTALLATION
a - Tilt pin (not included with engine)
a
2688
2749
Limits the down trim angle of the power
trim equipped engines, or aids in
determining the trim out angle on
non‑power trim engines.
138
17‑49930A 1
eng