Power Trim System; General Information; Power Trim Operation - Mercury 40 FourStroke Service Manual

Power Trim System

General Information

The power trim system is filled at the manufacturer and is ready for use.
Trim outboard through entire trim and tilt range several times to remove any air from the
system.
The trim system is pressurized and is not externally vented.

Power Trim Operation

With most boats, operating around the middle of the "trim" range will give satisfactory re-
sults. However, to take full advantage of the trimming capability there may be times when
you choose to trim your outboard all the way in or out. Along with an improvement in some
performance aspects comes a greater responsibility for the operator, and this is being aware
of some potential control hazards. The most significant control hazard is a pull or "torque"
that can be felt on the steering wheel or tiller handle. This steering torque results from the
outboard being trimmed so that the propeller shaft is not parallel to the water surface.
Avoid possible serious injury or death. When the outboard is trimmed in or out be-
yond a neutral steering condition, a pull on the steering wheel or tiller handle in ei-
ther direction may result. Failure to keep a continuous firm grip on the steering
wheel or tiller handle when this condition exists can result in loss of boat control
as the outboard can turn freely. The boat can now "spin out" or go into a very tight
maximum turn which, if unexpected, can result in occupants being thrown within
the boat or out of the boat.
Consider the following lists carefully:
TRIMMING IN OR DOWN CAN:
1. Lower the bow.
2. Result in quicker planing off, especially with a heavy load or a stern heavy boat.
3. Generally improve the ride in choppy water.
4. Increase steering torque or pull to the right (with the normal right hand rotation propel-
ler).
5. In excess, lower the bow of some boats to a point where they begin to plow with their
bow in the water while on plane. This can result in an unexpected turn in either direction
called "bow steering" or "over steering" if any turn is attempted or if a significant wave
is encountered.
Avoid possible serious injury or death. Adjust outboard to an intermediate trim po-
sition as soon as boat is on plane to avoid possible ejection due to boat spin-out.
Do not attempt to turn boat when on plane if outboard is trimmed extremely in or
down and there is a pull on the steering wheel or tiller handle.
TRIMMING OUT OR UP CAN:
1. Lift the bow higher out of the water.
2. Generally increase top speed.
3. Increase clearance over submerged objects or a shallow bottom.
90-857046R1 NOVEMBER 2001
WARNING
WARNING
GENERAL INFORMATION
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