2. OPERATING THE BOAT__PAGE 17
The engine trim is used to adjust the bow up or down (the so-called pitch) while the
boat is under speed. A well-adjusted engine trim will maximise safety and comfort, and
will minimise fuel consumption.
Mastering the trim requires some practice so if you are uncertain, ask someone
experienced for help. Correct trim is very important for a safe, comfortable and fuel
economic ride, and for fast acceleration.
The basic directions to find optimal trim are as follows, and shall be done during flat
water conditions:
Accelerate to planing speed (approximately 10 to 15 knots depending on
conditions):
Engine trim is used to help the boat accelerate as fast as possible from zero to
planing speed, with an optimal pitch. Fast acceleration to planing saves fuel and
improves the view.
Engine trim shall be at maximum trim down position directly at the start.
As the boat accelerates and reach planing speed, the trim is changed from the
trim down up to neutral trim, to keep the bow level or at a slight upward angle.
Failure to do so causes the bow to plough deep into the water, preventing the
boat to pick up speed and run safely.
Trim when running at speeds above planing:
When the boat is running at speeds above planing, the trim also needs to be
adjusted. As speed, direction, load, wind or wave conditions changes, new
adjustments may be required.
Use the trim up, to lift the bow up slowly without change of throttle position.
Follow the log to notice for how long the speed is increasing. When the speed is
not increasing anymore, the trim is in the most fuel-economic position. Then
lower the bow slightly to avoid the propeller loose grip.
In head sea (boat running against waves), you may have to use the trim to lower
the bow down to soften the vertical motions, but be careful not to lower it too
much due to the risk of a bow to plunge into waves.
In the following sea, you may instead need to raise the bow up to prevent nose-
diving.
A safe ride is always more important than maximising speed/fuel consumption, so
always trim for safety first.
Trim when lowering speed to below planing:
When you reduce speed below planning, or stop the boat completely, the trim
should again be adjusted to trim down position. This improves manoeuvrability
and makes the boat ready to accelerate fast next time.
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