Adjusting Boat Trim - Yamaha F30A Owner's Manual

Operation
3. Hold the rear of the top cowling with one
hand and tilt the engine to the desired
angle.
4. Place the tilt lock lever back into the lock
position to support the engine.
To raise the bow ("trim-out"), tilt the engine
up.
To lower the bow ("trim-in"), tilt the engine
down.
Make test runs with the trim set to different
angles to find the position that works best for
your boat and operating conditions.
EMU27911

Adjusting boat trim

When the boat is on plane, a bow-up attitude
results in less drag, greater stability and effi-
ciency. This is generally when the keel line of
the boat is up about 3 to 5 degrees. With the
bow up, the boat may have a greater tenden-
cy to steer to one side or the other. Compen-
sate for this as you steer. The trim tab can
also be adjusted to help offset this effect.
When the bow of the boat is down, it is easier
to accelerate from a standing start onto
plane.
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ZMU04061
Bow Up
Too much trim-out puts the bow of the boat
too high in the water. Performance and econ-
omy are decreased because the hull of the
boat is pushing the water and there is more
air drag. Excessive trim-out can also cause
the propeller to ventilate, which reduces per-
formance further, and the boat may "por-
poise" (hop in the water), which could throw
the operator and passengers overboard.
Bow Down
Too much trim-in causes the boat to "plow"
through the water, decreasing fuel economy
and making it hard to increase speed. Oper-
ating with excessive trim-in at higher speeds
also makes the boat unstable. Resistance at
the bow is greatly increased, heightening the
danger of "bow steering" and making opera-
tion difficult and dangerous.