Selectrim System

Chapter Sixteen
Selectrim System
This chapter covers removal and
installation of the mechanical and hydraulic
SelecTrim systems. Table 1 is at the end of
the chapter.
OPERATION
Trimming describes a change in the stem
drive unit's angle in the water relative to the
bottom of the boat. Moving the stem drive
away from the transom (trimming out) raises
the bow in the water; moving it toward the
transom (trimming in) lowers the bow.
Proper
trimming
assures
maximum
performance under given load and sp)eed
conditions.
Early OMC models are trimmed by
adjusting the engine mounts. Later models
may be equipped with a power trim system
called SelecTrim. On all inline and some
older V8 models fitted with SelecTrim, a
motorized jackscrew arrangement connected
to the front engine mount raises and lo^vers
the front of the engine to obtain the desired
trim angle. Models without SelecTrim use a
similar jackscrew front mount, with the trim
angle set manually.
All V6 and late-model V8 SelecTrim
models use an electro-hydraulic trim system.
An
electric
motor
operates
an
engine-mounted pump and reservoir to
provide pressure for raising or lowering the
hydraulic actuators under the forward motor
mounts.
The SelecTrim motor in both systems
contains an intemal circuit breaker. This
protects the motor from an overload
condition if the trim switch is held on after
the unit has completed its travel. The
SelecTrim system is also protected by the
same inline fuse that protects the power tilt
system.
MECHANICAL SYSTEM
Removal/Installation
If the system is inoperative for any reason,
use a hoist and chain connected to the engine
371
SELECTRIM SYSTEM
4. Remove the pillow block lag screws on
either side of the jackscrew bracket (Figure 1).
5. Operate the SelecTrim switch until the
front mounts clear the engine stringers.
6. If jackscrew pivot shaft is mounted to an
engine bracket, remove the snap ring from
the shaft end and drive pivot pin out with a
hammer and punch.
7. Disconnect the SelecTrim wiring.
8. Remove the jackscrew bracket bolts. See
Figure 2 (inhne) or Figure 3 (V6 and V8).
Remove the beam and backup plates
installed between the engine and engine
mount bracket.
9. Installation is the reverse of removal.
Tighten fasteners to specifications (Table 1).
Coat SelecTrim wire connections with OMC
Black Neoprene Dip. Operate system to full
HI and full LO positions to calibrate sending
unit.
Removal/Installation
(Inline Engine Bracket)
lifting brackets to raise and lower the engine
as required in this procedure.
1. Raise the front of the engine by moving
the SelecTrim switch to LO.
2. Insert a suitable length of 2X4 or other
appropriate blocking material under the
engine to provide support.
3. Move the SelecTrim switch to HI and
lower the engine until it just contacts the
support.
Refer to Figure 4 for this procedure.
1. Remove the 2 screws holding the rubber
mount to the bracket. Separate the bracket
from the jackscrew.
2. Push the rubber boot down below the hex
surface on the jackscrew.
3. Hold the jackscrew with an open-end
wrench and remove the locknut.
4. Remove the stop and rebound washers,
spacer, rubber mount and lower spacer from
the bracket.
5. Cut the tie strap at the bottom of the
rubber boot. Remove the rubber boot.
6. Installation is the reverse of removal.
Tighten all fasteners to specifications (Table
1).
Bracket Removal/Installation
(V8 Engine)
Refer to Figure 5 for this procedure.
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372
CHAPTER SIXTEEN
1. Remove the tie strap at the bottom of the
boot.
2. Rotate the bracket counterclockwdse until
the jackscrew is exposed. Clamp the
jackscrew in a vise with protective jaws.
3. Remove the roll pin andflangenut (Figure
6) from the jackscrew.
4. Remove the jackscrew from the vise.
Rotate the bracket counterclockwise and
remove from jackscrew.
5. Remove the boot retainer screws. Remove
the retainer and boot.
6. Separate the rubber mount from the
bracket with an arbor press.
7. Remove the mount retainer from the
jackscrew.
ENGINE MOUNT BRACKET
(V6 AND V8 MODELS)
ENGINE MOUNT BRACKET
(INLINE MODELS)
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
6.
7.
6.
9.
10.
11.
12.
13.
Backup plate
Locknut
Stopwasher
Rebound washer
Spacer
Lockwather
Bolt
Rubber mount
assembly
Screw
Spacer
Jackscrew
Rubber boot
Clamp
Pin
Flange nut
Rubber mount assembly
Bracket assembly
Retainer
6.
7.
8.
9.
10.
Jackscrew
Rubber boot
Boot retainer
Screw
Clamp
373
SELECTRIM SYSTEM
®
SELECTRIM
ASSEMBLY
8. Installation is the reverse of removal.
Tighten all fasteners securely.
SelecTrim Disassembly
1.
2.
3.
4.
Pillow block
Jackscrew
Boot
Trim sender
5. Mount bracket
6. Worm wheel cover
7. Motor
Refer to Figure 7 for this procedure.
1. Remove the engine bracket as described in
this chapter.
2. Invert the SelecTrim assembly bracket
and clamp the jackscrew in a vise with
protective jaws so that the assembly bracket
rests on the vise.
3. Remove the pillow block at each side of
the assembly bracket.
4. Unclamp and slide trim motor rubber
cover back until you have access to the
through bolts, if so equipped. Make
alignment marks on the drive end cap and
field assembly. Remove the through bolts.
NOTE
The motor field frame is sealed to the
end heads by cemented gaskets. If the
field frame separates from the drive end
head and armature in Step 5, see
Motor Reassembly in this chapter.
TRUNNrON HOUSING ASSEMBLY
1.
2.
3.
4.
Trunnion housing
Shim(s)
Thrust washer
Thrust bearing
5. Carefully separate motor from trunnion
housing.
6. Remove the O-dng seal from the motor
cavity on the trunnion housing.
7. Note position of wire clamp and remove
the SelecTrim sender from the assembly
bracket (Figure 8).
8. Remove the trunnion housing cover
screws. Remove the cover.
9. Reach into the trunnion housing and
remove the first thrust washer, thrust bearing,
second thrust washer and shim(s) in that
order. See Figure 9.
10. Remove the worm gear, thrust bearing,
thrust washer and shim from the trunnion
housing. See Figure 10.
11. Remove the bolt, washers and spacers
from the end of the jackscrew. See Figure 11.
16
374
12. Unscrew and remove worm wheel from
assembly bracket. Remove bracket from
jackscrew.
13. Remove jackscrew from vise and clamp
bracket in its place.
14. Remove lower bearing from inside of
bracket with puller part No. 391010.
15. Remove a thrust washer, thrust bearing,
thrust washer and shim(s) from the braclcet
bore.
16. Install puller part No. 391010 and
remove upper bearing from bracket bore.
17. Remove assembly bracket from vise.
18. Clean all parts in solvent and blow dry
with compressed air. Replace any
components that are corroded, wom or
damaged.
CHAPTER SIXTEEN
WORM GEAR ASSEMBLY
1. Trunnion housing
3. Shim(s)
4. Thrust washer
5. Thrust bearing
6. Worm gear
Socket
SelecTrim Assembly
Refer to Figure 7 for this procedure.
1. Install upper bearing in assembly bracket
(letter side up) with installer part No. 907990
and a suitable driver.
2. Sandwich the thrust bearing between the
thrust washers and install in the assembly
bracket bearing cavity.
3. Install the worm wheel and position
shimming gauge part No. 907988 as shown in
Figure 12. Measure the gap between the
worm wheel and gauge with a flat feeler gauge
to determine the required shim thickness.
4. Remove the worm wheel and thrust
bearing sandwich. Install the shimL(s)
determined in Step 3, then reinstall the thrast
bearing sandwich.
5. Install lower bearing in assembly bracket
(letter side up) v^th installer part No. 907989
and a suitable driver.
6. Clamp jackscrew with its large diameter
end facing up in a vise with protective jaws.
Coat jackscrew threads with OMC Extreme
Pressure Grease and screw worm wheel onto
jackscrew.
Two flat washers
with spring
washer between
Special toot 907988
375
SELECTRIM SYSTEM
Special tool
907986
7. Sandwich the 6 spring washers between
the 2 flat washers and install on worm wheel
with spacer and boh. See Figure 11. Tighten
bolt to specifications (Table 1).
8. Remove jackscrew from vise and install
assembly bracket in its place with the large
bore facing upward. Install a new O-ring in
the bracket groove.
9. Install the worm gear thrust washer and
bearing in the trunnion housing bore, then
install the worm gear. See Figure 10.
10. Position shimming gauge part No.
907987 as shown in Figure 13 and measure
with a flat feeler gauge.
11. Remove the thrust washer and bearing
from the trunnion housing bore. Install
shim(s) equal to the measurement in Step 10,
then reinstall the thrust washer and bearing.
12. Sandwich the trunnion housing thrust
bearing between the thrust washers and
install in the housing. See Figure 9.
13. Position shimming gauge part No.
907986 as shown in Figure 14 and measure
with a flat feeler gauge.
14. Remove the thrust bearing sandwich
from the trunnion housing bore. Install
shim(s) equal to the measurement in Step 13,
then coat the thrust bearing sandwich with
OMC Extreme Pressure Grease and reinstall
in the bore.
15. Apply a light coat of OMC Extreme
Pressure Grease to the worm wheel gear
teeth. Install the trunnion on the assembly
bracket and tighten bolts to specifications
(Table 1).
16. Position a new O-ring in the sender unit
cover groove. Lubricate the sending unit gear
with OMC Extreme Pressure Grease and
install to the assembly bracket.
17. Install a new O-dng in the trim motor
cavity. Install the trim motor.
18. Check unit operation by connecting tdm
leads to a 12-volt battery. If the unit operates
properly, reinstall in the boat as described in
this chapter.
Motor Reassembly
Under certain conditions, it is possible that
the tilt motor field frame will separate from
the drive end cap during removal from the
assembly bracket trunnion housing. Use the
following procedure to avoid a complete and
unnecessary disassembly of the tilt motor.
1. Carefully place field frame assembly on a
clean workbench.
2. Remove the drive end cap and armature
from the trunnion housing bore.
16
CHAPTER SIXTEEN
376
3. If drive end cap gasket is damaged,
remove all remnants of old gasket. Clean
mating surfaces thoroughly of all residue and
install a new gasket coated on both sides 'mXh
OMC Gasket Sealing Compound.
4. Carefully separate the commutator end
cap from the field frame without pulling the
brush leads off.
5. Repeat Step 3 if commutator end cap
gasket is damaged.
6. Install armature and drive end cap to the
field frame.
7. Position commutator end cap to
commutator and push brushes out of the way
with a pencil as cap is installed.
8. Install through bolts. Thread suitable nuts
on bolt ends to hold assembly together until it
is installed to the trunnion bore.
HYDRAULIC SYSTEM
Hydraulic Fluid
The hydraulic system requires a total of 14
ounces of fluid. Pumps used with P^ord
engines should be filled with OMC Sea-Lube
Premium Blend Gearcase Lubricant. Pumps
used with GM engines are filled with OMC
Power Trim and Tilt fluid.
A certain amount of hydraulic fluid is lost
whenever a hydraulic fitting is opened for
pump or tilt cylinder service. Use the
following procedure to replace the lost fluid.
1. Remove fill plug (Figure 15, typical) and
top ofl* the reservoir with the proper fluid.
2. Run trim motor and extend piston rods.
Add fluid as rods extend.
3. Install fill plug.
4. Run trim motor to retract and fully extend
piston rod. Remove fill plug, top up reserv^oir
and install plug.
5. Repeat Step 4 at least 4 times or until
reservoir requires no additional fluid with
piston rods fully extended.
6. Test pump operation. With a fully charged
battery, the engine should reach its fully up
position in 9-13 seconds and return to a fully
down position in no more than 8 1/2 seconds.
Hydraulic Pump
Removal/Installation
1. Disconnect the negative battery cable.
2. Disconnect
the
pump
electrical
connectors.
3. Place a container or rag under the pump
hydraulic line connections. See Figure 15
(typical).
4. Mark the hydraulic lines at the pump for
correct reinstallation. Disconnect and cap the
lines.
5A. V6 models—disconnect the negative
battery cable from the retainer stud. Remove
the pump retainer nut and lockwasher from
the stud. Remove the 2 pump screws and
lockwashers. Remove the pump.
5B. GM V8 models—remove the retaining
screws and lockwashers. Remove the pump.
5C. Ford models—remove the pump
attaching screws. Remove the pump.
6. Installation is the reverse of removal.
Tighten all fasteners to specifications (Table
1).
Trim Cylinder
Removal/Installation
The following procedures are for trim
cylinder removal with the engine in the boat.