Preliminary Checks; Leak Down Check - Pump And Manifold Assembly - Mercury 75 Service Manual

Preliminary Checks

Operate Power Trim System after each check to see
if problem is corrected. If not, proceed with the 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 "Fill
and Purge the Power Trim System."
3. Check for external leaks in Power Trim system.
Replace defective part(s) if leak is found.
4. Outboard not holding tilted position (falls to trim
in position) indicates debris or defective compo-
nents 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.
Leak Down Check - Pump and
Manifold Assembly
The 1993 and 1994 models listed with power trim
date codes 13011 through 23288 ONLY may experi-
ence a very slow trim rate (one minute or more) with
the outboard drifting back down as soon as the UP
trim button is released. This failure usually occurs
when the unit is new or after 3 or 4 weeks of non use.
The cause may be a stuck spool inside the sleeve
due to an oversize or a hard O-ring on the spool
(SERVICE BULLETIN No. 93-22A).
NOTE: Scribe pump housing and manifold before
disassembly.
1. Remove tilt cylinder from the manifold and re-
place pilot valve assembly.
a
a - Sleeve with Spool Inside
5B-8 - MID-SECTION
2. The spool is considered stuck when the pin end
is protruding out past the end of the sleeve.
a - Spool Pin
Pilot Valve and Seat Removal
a - Pilot Valve
b - Valve Seat
c - Return Spring
d - Sleeve
e - Spool
50999
SPOOL STUCK
SPOOL NOT STUCK
a b c d
90-830234R3 DECEMBER 1997
a
52790
52791
e