Power Trim - General Information; Description; Trimming Characteristics; Trimming Outboard "Up" (Out) - Mariner 70 Service Manual

Power Trim - General
Information

Description

The Power Trim System consists of an electric motor,
pressurized fluid reservoir, pump, tilt cylinder, and two
trim rams.
The remote control (or trim panel) has switches that
trim the outboard "Up" or "Down" and tilt the engine for
"Trailering". The outboard can be trimmed and tilted
under power or when the outboard is not running.

Trimming Characteristics

NOTE: Because hull designs react differently in
varying water conditions, varying the trim position will
often improve the ride and boat handling. When
trimming from a mid-trim position (with outboard trim
tab in a straight fore and aft position), expect the
following:

TRIMMING OUTBOARD "UP" (OUT):

WARNING
Excessive trim "Out" may reduce the stability of
some high speed hulls. To correct instability,
reduce the power gradually and trim the outboard
"In" slightly before
operation. A rapid reduction in power will result in
a sudden change of steering torque and may
cause additional boat instability.
Will lift boat bow, increasing top speed.
Transfers steering torque harder to port (left) on in-
stallations above 23 in. transom height.
Increases gearcase clearance over submerged ob-
jects.
Excess trim can cause
ventilation.
WARNING
Excessive outboard trim angle will result in
insufficient water supply causing water pump
and/or powerhead overheating damage. Insure
water level is above water intake holes whenever
outboard is running.
90-13645--2 495
resuming high speed
"porpoising" and/or
POWER TRIM
The "Up" circuit actuates the "up" solenoid (under out-
board cowl) and closes the motor circuit. The electric
motor drives the pump, forcing fluid thru passage-
ways into the "up" side of the trim cylinders.
The trim cylinders position the outboard at the desired
trim angle in the 20 degree maximum trim range. The
system will not allow the outboard to be trimmed
above the 20 degree trim range as long as the engine
RPM is above approximately 2000 RPM.
The outboard can be trimmed above the 20 degree
maximum trim angle (for shallow water operation,
etc.), by keeping the engine RPM below 2000. If the
RPM increases over 2000, propeller thrust (if propel-
ler is deep enough) will result in the trim system to re-
turn the outboard to the 20 degree maximum trim po-
sition.

TRIMMING OUTBOARD "DOWN" (IN):

WARNING
Excessive speed at minimum trim "In" may result
in undesirable and/or unsafe steering conditions.
Test for handling characteristics after any
adjustment is made to the trim angle (and tilt pin
location).
Aids planing, particularly with heavy loads.
Improves ride in choppy water conditions.
Excess trim "In" can cause "bow steer" (boat veers to
left or right).
Transfers steering torque to starboard (right).
Improves acceleration to planing speed.
The "Down" circuit actuates the "down" solenoid (un-
der engine cowl) and closes the motor circuit. The
electric motor drives the pump in the opposite direc-
tion as the "up" circuit, forcing fluid thru passageways
into the "down" side of the tilt ram. The tilt ram moves
the engine down to the desired position.

Trailering Outboard

The "Up" circuit first moves the trim cylinders; when
the trim cylinders extend fully, the tilt ram extends to
tilt the outboard to the full "Up" position for trailering.
Before the boat is trailered, the operator should check
for clearance between the outboard skeg and pave-
ment to prevent damage to skeg from striking pave-
ment.
If the outboard must be tilted for clearance between
skeg and pavement, a device such as a "Transom
Saver" should be installed to prevent stress to boat
transom from outboard weight while the boat/out-
board are being trailered.
6A-1