Mariner Mercury 105/140 JET, Service Manual

Page: 48 / 797

90-824052R3 JUNE 2002 IMPORTANT INFORMATION - 1D-13
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 results. 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 respon-
sibility for the operator, and this is being aware of
some potential control hazards.The most significant
of which is a pull or “torque” which can be felt on the
steering wheel. This steering torque results from the
outboard being trimmed so that the propeller shaft is
not in a horizontal position.
WARNING
Avoid possible serious injury or death. When the
outboard is trimmed in or out beyond a neutral
steering condition, a pull on the steering wheel in
either direction may result. Failure to keep a
continuous firm grip on the steering wheel when
this condition exists can result in loss of boat
control as the steering wheel can spin 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 improves the ride in choppy water.
4. Increase steering torque or pull to the right (with
the normal right hand rotation propeller).
5. In excess, lowers the bow of some boats to a point
where they begin to plow with their bow in the wa-
ter while on plane. This can result in an unex-
pected turn in either direction called “bow steer-
ing” or “over steering” if any turn is attempted or if
a significant wave is encountered.
WARNING
Avoid possible serious injury or death. Adjust
outboard to an intermediate trim position 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.
Trimming Out or Up Can:
1. Lift the bow out of the water.
2. Generally increase top speed.
3. Increase clearance over submerged objects or a
shallow bottom.
4. Increase steering torque or pull to the left at a nor-
mal installation height (with the normal right hand
rotation propeller).
5. In excess, cause boat “porpoising” (bouncing) or
propeller ventilation.
6. Cause engine overheating if any water intake
holes are above the water line.