TROUBLESHOOTING
SERVICE MANUAL NUMBER 28
90-863160 MAY 2000 Page 1C-17
Power Trim Hydraulic System
NOTE:Refer to “Power Trim Hydraulic Schematic.”
Drive Unit Cannot Be Trimmed OUT/UP Or Trims Slowly Or With Jerky
Movements
Cause Special Instructions
Power trim pump oil level low.
Check for cause of low oil level and
correct. Add oil and bleed trim system.
Air in trim system.
Check for cause of entry and correct.
Add oil to pump and bleed air from
system.
O-rings damaged on Manual Release
Valve (if equipped) or valve not
completely closed.
Replace valve and/or close completely.
Insufficient pump pressure or pump.
shuttle valve stuck.
Test. If shuttle 1 is stuck, replace
pump adaptor (Refer to SECTION 5A). If
pressure is low, replace adaptor or
attempt to repair by replacing the
following components:
D OUT/UP Pressure Relief Valve
D Thermal Relief Valve
Hoses reversed on one cylinder only. Connect hoses 7 and 8 correctly.
Trim cylinder(s) binding.
Check for cause of binding (bent
piston rod, scored cylinder).
Repair or replace as necessary.
Gimbal housing-to-trim pump hydraulic
hose pinched.
Replace hose 7.
Up pressure relief valve has dirt
particles under check ball.
Replace with a new valve kit.
Drive Unit Will Not Stay In Trimmed OUT/UP Position
Cause Special Instructions
Air in trim system.
Check for cause of entry. Fill and bleed
system.
Shuttle valve (poppet valve).
Check for dirt. Install new poppet
valve.
Sterndrive Unit Trails OUT/UP On Deceleration Or When Shifting Into Reverse
UNIT THUMPS WHEN SHIFTING
Cause Special Instructions
Trim pump IN/DOWN circuit leaking
internally.
Test according to appropriate service
manual. Replace adaptor or attempt to
repair by replacing the pilot check
valves or seals. (Install Trim Pump
Rebuild Kit)
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