Hydraulic System Troubleshooting; Preliminary Checks; Leak Down Check - Pump And Manifold - Mercury 45 Jet 50-55 Service Manual

Hydraulic System Troubleshooting

Support outboard with tilt lock lever when servicing
power trim system.
IMPORTANT: After debris or failed components
have been found (during troubleshooting proce-
dure) it is recommended that unit be disas-
sembled completely and ALL O-rings be re-
placed. Check ball valve components and
castings must be cleaned using engine cleaner
and compressed air or replaced prior to reas-
sembly.
IMPORTANT: Power trim system is pressurized.
Outboard must be in the full "UP" position (trim
rod fully extended) prior to fill/drain plug, or man-
ual release valve removal.
Refer to instructions following if disassembly is re-
quired when servicing.
Follow preliminary checks before proceeding to trou-
bleshooting flow diagrams (following).

Preliminary Checks

IMPORTANT: Operate Power Trim system after
each check to see if problem has been corrected.
If problem has not been corrected proceed to next
check.
1. Check that manual release valve is tightened to
full right (clockwise) position.
2. Check trim pump fluid level with outboard in full
"UP" position and fill if necessary. Refer to "Bleed-
ing Power Trim Unit".
3. Check for external leaks in Power Trim system.
Replace defective part(s) if leak is found.
4. Outboard not holding tilted position (falls down to
trim position) indicates debris or defective com-
ponents in trim valve assembly. Clean or replace
components as required.
5. Check manual release valve for broken stem and
one O-ring remaining in the release valve pas-
sage. (Separate the manifold assembly from the
cylinder to dislodge broken stem.) Install new re-
lease valve and test system.
6. Check for nicked, deteriorated or misplaced O-
rings throughout trim system.
5C-12 - MID-SECTION
Leak Down Check – Pump and Man-
ifold Assembly
NOTE: Scribe (d) pump housing halves before disas-
sembly. Check pump for problems as follows:
1. Debris or chips between valve and seat (a). Usu-
ally imbedded in rubber valve seat.
2. Nicked or deteriorated O-ring (b).
3. Nicked, deteriorated or misplaced O-ring be-
tween manifold and trim cylinder. Refer to "Man-
ifold Removal" for O-ring location.
d
b
a
b
d
4. After reassembly, insert drive shaft and check
pump rotation resistance to turning – housing
halves can shift/turn during reassembly. Align
scribe marks (d) carefully.
51736
51735
90-8i7643R1 DECEMBER 1996