Trailer Position; Selecting The Correct Profile; What Trim Is; How Trim Affects Boat Operation - Mercury 71712 Operation Manual

Trailer Position

Placing the engine or drive in trailer position—over 50% of the adapted trim range, will prevent Active Trim from engaging. Any
time the engine or drive is trimmed above its normal range—to navigate shallow water, launch the boat from a trailer, or load
the boat onto a trailer, for example—you must manually trim down before Active Trim will function. This safety feature is meant
to prevent the engine or drive from automatically trimming down and hitting something.

Selecting the Correct Profile

With so many available trim profiles, it can be difficult to determine which profile is the correct one. In making this
determination, it is important to understand what trim is, how it affects boat operation, and how boat loading can influence the
required trim angle. Armed with a clear understanding of these concepts, selecting the correct trim profile becomes simple.

What Trim Is

The trim angle of an outboard or sterndrive is the angle between the boat bottom and the propeller shaft formed by moving the
engine or sterndrive closer to the boat transom. This movement is called trimming in or down. Moving the engine or sterndrive
further away from the transom is called trimming out or up. When a boat is cruising on plane and the trim is adjusted so that the
propeller shaft is parallel to the surface of the water, that is said to be running at zero trim.
The term "trim" is generally used when referring to adjusting the outboard or sterndrive within the first 20° range of travel. This
is the range used while operating your boat on plane. The term "tilt" is generally used when referring to adjusting the outboard
or sterndrive further up or out of the water.

How Trim Affects Boat Operation

The trim angle of the outboard or sterndrive has a distinct effect on the planing angle of the boat, which in turn significantly
alters the top speed and handling. The engine or drive should be trimmed in for best start‑up acceleration and shortest time to
plane. The engine or drive would then be trimmed out for peak performance. Active Trim automatically handles this transition
for you.
If the engine or drive is trimmed in too far, the bow drops and the boat runs too wet. In this condition, top speed drops, fuel
economy decreases, the boat may oversteer in one direction or the other (bow steering), and steering torque will increase (to
the right with a right‑hand rotation propeller). Occasionally, extreme trim down can cause a boat to list to the left (with a
right‑hand propeller).
If the engine or drive is trimmed out too far, the propeller may lose its hold on the water, fast V‑bottom boats may start to walk
from side to side (chine walking), steering torque will increase in the opposite direction to that when trimmed in, and getting on
plane may be difficult or labored. Porpoising of the boat may also occur.
90-8M0180922 MAY 2021
eng
Engine or drive properly trimmed
Engine or drive trimmed in (bow too low)
Engine or drive trimmed out (bow too high); porpoising
Section 1 - DTS Controls and Features
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