Mercury OptiMax 250 User manual

3
B
DIRECT FUEL INJECTION
Page 3B-1
90-888438 JUNE 2002
FUEL SYSTEM
Section 3B – Direct Fuel Injection
Table of Contents
Specifications 3B-2. . . . . . . . . . . . . . . . . . . . . . . . . . .
Special Tools 3B-3. . . . . . . . . . . . . . . . . . . . . . . . . . .
Notes: 3B-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Handler 3B-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Handler Components 3B-8. . . . . . . . . . . . . . . . .
Air Handler Components 3B-10. . . . . . . . . . . . . . . . .
Vapor Separator Components 3B-12. . . . . . . . . . . . .
Fuel Rails 3B-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Compressor Components 3B-16. . . . . . . . . . . . .
DFI Operation 3B-18. . . . . . . . . . . . . . . . . . . . . . . . . .
Air Induction Through Crankcase 3B-18. . . . . . .
Air Compressor System 3B-18. . . . . . . . . . . . . . .
Fuel 3B-18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil 3B-19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical 3B-19. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operation 3B-19. . . . . . . . . . . . . . . . . . . . . . . . . . .
Testing Electric Fuel Pump Pressure Output 3B-20
Low Pressure Electric Fuel Pump 3B-20. . . . . . .
High Pressure Electric Fuel Pump 3B-21. . . . . .
Fuel Management Assembly Removal 3B-22. . . . .
Reed Block Assembly Removal 3B-25. . . . . . . .
Reed Block Assembly Installation 3B-25. . . . . . .
Air Temperature Sensor Removal 3B-26. . . . . .
Air Temperature Sensor Installation 3B-26. . . . .
Throttle Plate Assembly Removal 3B-26. . . . . . .
Throttle Plate Assembly Installation 3B-26. . . . .
Vapor Separator Disassembly 3B-27. . . . . . . . . .
Vapor Separator Reassembly 3B-29. . . . . . . . . .
Air Plenum Installation 3B-30. . . . . . . . . . . . . . . .
Low Pressure Electric Fuel Pump Installation . ..
3B-30
Vapor Separator Installation 3B-33. . . . . . . . . . .
Fuel Rail Removal 3B-35. . . . . . . . . . . . . . . . . . . .
Fuel Pressure Regulator 3B-40. . . . . . . . . . . . . .
Air Pressure Regulator 3B-43. . . . . . . . . . . . . . . .
Air Regulator Troubleshooting 3B-43. . . . . . . . . . 3B-44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tracker Valve 3B-46. . . . . . . . . . . . . . . . . . . . . . . .
Fuel Rail Cleaning 3B-49. . . . . . . . . . . . . . . . . . . .
Direct Injector Removal 3B-49. . . . . . . . . . . . . . .
Direct Injector Leak Test 3B-50. . . . . . . . . . . . . . .
Fuel Rail and Direct Injector Installation 3B-51.
Air Compressor 3B-52. . . . . . . . . . . . . . . . . . . . . .
Air Compressor Disassembly/Reassembly 3B-55
Air Compressor End Cap/Crankshaft Removal and
Reassembly 3B-56. . . . . . . . . . . . . . . . . . . . . . . . .
Air Compressor Flow Diagram 3B-59. . . . . . . . .
Air Compressor Pressure Test 3B-60. . . . . . . . .

DIRECT FUEL INJECTION
Page 3B-2 90-888438 JUNE 2002
Specifications
Fuel System Specifications
Fuel Pressure 90 ±2 psi (613.5 ±13.8 kPa)
Air Pressure 80 ±2 psi (544.0 ±13.8 kPa)
Fuel/Air Differential 10 psi (68.5 kPa)
High Pressure Electric Fuel Pump Amperage
Draw 6-9 Amps
Low Pressure Electric Fuel Pump Amperage
Draw 1-2 Amps
Low Pressure Electric Fuel Pump Output 6-10 psi (41.37 kPa - 68.95 kPa)
Fuel Injector Ohm Resistance 1.8 ±0.1Ω
Direct Injector Ohm Resistance 1.3 ±0.3Ω
Fuel Lift Electric Fuel Pump
Output 1-10 psi (68.5 kPa)
Air Compressor Specifications
Air Compressor Type
Compressor Output
Reciprocating Piston
(1 to 1 ratio with engine RPM)
@ Idle – 80 psi
@ W.O.T. – 110 psi
Cylinder Block Displacement 7.07 cu. in. (116 cc)
Cylinder Bore Diameter (Standard)
Taper/Out-of-Round/Wear Maxi-
mum
Bore Type
2.5591 in. (65.0 mm)
0.001 in. (0.025 mm)
Cast Iron
Stroke Length 1.374 in. (34.9 mm)
Piston Piston Type Aluminum
Piston Diameter
Dimen-
sion “A”
at Right
Angle
(90°) to
Piston Pin
0.500 in.
2.5578 ±.0004 in.
(64.97 ±0.010 mm)
Piston Ring End Gap
Top Ring
Middle Ring
Bottom Ring
0.0059 - 0.0098 in.
(0.15 - 0.25 mm)
0.0059 - 0.0098 in.
(0.15 - 0.25 mm)
0.0039 - 0.014 in.
(0.10 - 0.35 mm)
Reeds Reed Stand Open 0.010 in. (0.25 mm)

DIRECT FUEL INJECTION
Page 3B-3
90-888438 JUNE 2002
Special Tools
1. Duel Fuel/Air Pressure Gauge 160 psi – 91-852087A1/A2/A3
a
57818
a-Schrader Valve “Tee” (22-849606)
2. Adaptors to convert pressure gauge 91-852087A1/A2 to an A23
NOTE: 2 Adaptors 91-803804A2 are required to convert a pressure gauge set.
abcd
a-1/2 in. to 1/4 in. Adapter (if required)
b-Female Quick Disconnect
c-Male Quick Disconnect
d-Screw on Schrader
3. Screw (5 mm x 25 mm) (2 each) – 10-40073-25
4. Flat Washer (2 each) – 12-30164
5. Seal/Teflon Ring Installation Tool – 91-851980
56015
6. Seal/Teflon Ring Sizing Tool – 91-851980-1
56014

DIRECT FUEL INJECTION
Page 3B-4 90-888438 JUNE 2002
7. DMT 2000 Digital Tachometer Multi-meter P/N 91-854009A1
8. Clamp Tool Kit 91-803146A2
57316
a
a-Clamp Tool 91-803146T
9. Gearcase Leakage Tester (FT-8950)
57714

DIRECT FUEL INJECTION
Page 3B-5
90-888438 JUNE 2002
Notes:

DIRECT FUEL INJECTION
Page 3B-6 90-888438 JUNE 2002
Air Handler
25 Liquid Neoprene
25

DIRECT FUEL INJECTION
Page 3B-7
90-888438 JUNE 2002
Air Handler
REF
TORQUE
REF
.
NO. QTY. DESCRIPTION lb-in lb-ft Nm.
1 1 AIR HANDLER ASSEMBLY
2 1 VAPOR SEPARATOR ASSEMBLY
3 2 CLAMP (18.3)
4 AR HOSE (22 IN. Bulk)
5 1 FUEL PUMP ASSEMBLY
6 1 FILTER-Fuel Pump
7 1 SCREW (M6 x 35) 100 11.3
8 1 BRACKET-Fuel Pump Mount
9 4 CLAMP (18.3)
10 1 HOSE
11 AR INSULATING SLEEVE
12 1 ELBOW
13 1 O RING
14 1 FUEL PUMP ASSEMBLY
15 1 SLEEVE-Gray
16 1 BRACKET KIT
17 1 GROMMET
18 3 SCREW (M6 x 16) 100 11.3
19 1 O RING
20 1 FITTING 45 5.1
21 1 HOSE
22 1 WIRE ASSEMBLY-Ground
23 1SCREW (M6 x 10) 40 4.5
24 1 CABLE TIE (14 IN.)
25 3 DECAL-Info
NOTE: THE EPA LABEL HAS IMPORTANT INFORMATION ON EPA EMISSION REGULATIONS. REPLACE ANY
MISSING OR UNREADABLE EPA LABEL.

DIRECT FUEL INJECTION
Page 3B-8 90-888438 JUNE 2002
Air Handler Components

DIRECT FUEL INJECTION
Page 3B-9
90-888438 JUNE 2002
Air Handler Components
REF
TORQUE
REF
.
NO. QTY. DESCRIPTION lb-in lb-ft Nm.
– 1 AIR HANDLER
1 1 ADAPTOR PLATE
2 1 GASKET
3 6 REED BLOCK
4 12 SCREW (M6 x 1) 90 10.2
5 3 BUSHING
6 3 GROMMET
7 3 WASHER
8 3 SCREW (M8 x 30) 150 17
9 1 AIR PLENUM KIT
10 1 GASKET
11 2SCREW (M4 x 16) 22 2.5
12 1 SENSOR–MAP
13 1 BRACKET
14 1 TEMPERATURE SENSOR
15 1O RING
16 1 THROTTLE BODY KIT
17 4 SCREW (M6 x 40) 65 7.3
18 1 O RING
19 1 OIL PUMP
20 1 ROLLER
21 1 THROTTLE ROLLER
22 1 SCREW 22 2.5
23 1 WASHER-Cupped
24 1 WASHER-Spool
25 1 LOCKWASHER (#10 External)
26 1RETAINING RING
27 2RETAINER-Hose Support
28 1 CLAMP
29 6 CHECK VALVE 40 4.5
30 1SCREW (M6 x 16) 38 4.3
31 1 FILTER ASSEMBLY-Air
32 12 SCREW (M6 x 40) 120 13.6
33 2 WASHER
34 1 COVER ASSEMBLY-Flywheel
35 3 GROMMET
36 1 PLUG
37 2 GROMMET
38 1 ATTENUATOR ASSEMBLY-Air
39 1 BUSHING
40 1 GROMMET

DIRECT FUEL INJECTION
Page 3B-10 90-888438 JUNE 2002
Air Handler Components

DIRECT FUEL INJECTION
Page 3B-11
90-888438 JUNE 2002
Air Handler Components
REF
TORQUE
REF
.
NO. QTY. DESCRIPTION lb-in lb-ft Nm.
41 1 SEAL
42 1 GROMMET
43 1 CLIP
44 1 SCREW (#10-16 X .750)
45 1 CLAMP
46 1 SCREW (M6 X 25) 90 10.2
47 1 WASHER
48 1 DECAL-Logo (M2 Jet Drive)
49 1 DECAL-Logo (3.0l V6)
50 1 DECAL-Logo (Mercury Optimax 250)
51 1DECAL-EPA Label Info

DIRECT FUEL INJECTION
Page 3B-12 90-888438 JUNE 2002
Vapor Separator Components

DIRECT FUEL INJECTION
Page 3B-13
90-888438 JUNE 2002
Vapor Separator Components
REF
TORQUE
REF
.
NO. QTY. DESCRIPTION lb. in. lb. ft. N·m
1 1 COVER KIT
2 1 FITTING-Straight 65 7.3
3 1 FITTING-Elbow 50 5.7
4 1 SEAL
5 1 FITTING KIT-Pump Outlet 75 8.5
6 1 O RING
7 7 SCREW (#8-32 x .750) 22 2.5
8 1 GASKET
9 1 FLOAT KIT
10 1 SHAFT-Float
11 1NEEDLE VALVE
12 1 SCREW (#6-32 x .187) 10 1.0
13 1 FUEL PUMP ASSEMBLY
14 1 SLEEVE
15 1 BOWL KIT
16 1 SEAL
17 1 PLUG KIT
18 1 O-RING
19 1 FITTING-Elbow 65 7.3
20 1 FITTING-Elbow 65 7.3
21 1 FITTING-Elbow 65 7.3
22 1 FUEL FILTER KIT
23 1 PROBE-Water Sensing 22 2.5
24 1PLUG (.125-27)
25 3 BUSHING
26 6 WASHER
27 3 GROMMET
28 3 SCREW (M8 X 35)

DIRECT FUEL INJECTION
Page 3B-14 90-888438 JUNE 2002
Fuel Rails

DIRECT FUEL INJECTION
Page 3B-15
90-888438 JUNE 2002
Fuel Rails
REF
TORQUE
REF
.
NO. QTY. DESCRIPTION lb-in lb-ft Nm.
1 6 AIR INJECTOR KIT
2 6 WASHER ASSEMBLY-Cupped
3 1 FUEL RAIL (PORT)
4 1 FUEL RAIL (STARBOARD)
5 1 FITTING
6 1 O-RING KIT
7 4 CLAMP
8 15 SCREW (M5 x 8) 70 8
9 2 CAP
10 1 FUEL VALVE KIT
11 1O-RING KIT
12 4 SCREW (M5 x 16) 70 8
13 1 COVER
14 1 SPRING
15 1 O-RING
16 1 DIAPHRAGM
17 1 FITTING
18 2 CLAMP
19 1 CLAMP
20 1 AIR VALVE ASSEMBLY
21 4 CLAMP
22 1 O-RING KIT
23 1 O-RING KIT
24 1 AIR PLUG
25 1 ELBOW
26 6 FUEL INJECTOR
27 1 SEAL
28 1 HOSE ASSEMBLY-Air Balance
29 1 HOSE ASSEMBLY-Fuel Balance
30 1 HOSE ASSEMBLY-Fuel Supply
31 1HOSE ASSEMBLY-Air By Pass
32 1HOSE ASSEMBLY-Fuel By Pass
33 2CLAMP (18.3)
34 4 STUD (M10 x 91)
35 4 NUT (M10)
36 1 SCREW (M5 x 35)
37 1 CLAMP-Hose Support
38 4 CLIP-Conduit Support
39 1 CLAMP-Worm Gear

DIRECT FUEL INJECTION
Page 3B-16 90-888438 JUNE 2002
Air Compressor Components
7Loctite 271

DIRECT FUEL INJECTION
Page 3B-17
90-888438 JUNE 2002
Air Compressor Components
REF
TORQUE
REF
.
NO. QTY. DESCRIPTION lb-in lb-ft Nm.
1 1 AIR COMPRESSOR
2 1 END CAP
3 1 RING-Retaining
4 4 SCREW (M6 X 20) 100 11.3
5 1 O RING
6 1 O RING
7 1 CONNECTING ROD
8 1 PISTON ASSEMBLY
9 2 LOCK RING
10 1REED PLATE ASSEMBLY
11 2O RING
12 1 O RING
13 1 SEAL
14 1 COMPRESSOR HEAD KIT
15 1 FITTING 25 33.9
16 4 SCREW (M8 x 35) See Note
17 1 ELBOW
18 1 ELBOW
19 2 CHECK VALVE
20 1 FITTING 25 33.9
21 1 FITTING
22 1 O RING
23 1 TEMPERATURE SENSOR
24 1 RETAINER
25 1 SCREW (M8 x 14) 150 17
26 1 PIN 45 5.1
27 6 SCREW (M6 x 12) 14-15 19-
20.3
28 1 PULLEY
29 4 SCREW (M8 x 50) 20 27.1
30 4 CABLE TIE (8 IN.)
31 1 HOSE
32 1 HOSE ASSEMBLY
33 2 CLAMP (15.3)
NOTE: Item #16 - Torque screws to 27.1 Nm (240 lb-in.), plus 90 degree turn

DIRECT FUEL INJECTION
Page 3B-18 90-888438 JUNE 2002
DFI Operation
Air Induction Through Crankcase
Once inside the enclosure the air enters the plenum through the throttle shutter which is
located in the plenum assembly. The air then continues through the reed valves and into
the crankcase. The throttle shutter is actuated by the throttle shaft. Mounted on a separate
shaft is a throttle position sensor (TPS). This sensor tells the engine control unit (ECM)
the position of the throttle.
If the TPS should fail, the warning horn will sound. Engine speed will be reduced.
Air Compressor System
Air from inside the engine enclosure is drawn into the compressor through the air attenua-
tor. This attenuator acts like a muffler to quiet compressor noise and contains a filter to
prevent the ingestion of debris into the compressor. The compressor is driven by a belt
from a pulley mounted on the flywheel and is automatically self adjusted using a single
idler pulley. This air compressor is a single cylinder unit containing a connecting rod, pis-
ton, rings, bearings, reed valves, and a crankshaft. The compressor is water cooled to
lower the temperature of the air charge and is lubricated by oil from the engine oil pump
assembly. As the compressor piston moves downward inside the cylinder, air is pulled
through the filter, reed valves and into the cylinder. After the compressor piston changes
direction, the intake reeds close and the exhaust reeds open allowing compressed air into
the hose leading to the air/fuel rails.
The air/fuel rails contain two passages; one for fuel, the second is the air passage. The
air passage is common between all the cylinders included in the rail. A hose connects the
starboard rail air passage to the air compressor. Another hose connects the starboard air
rail passage to the port air rail passage. An air pressure regulator will limit the amount of
pressure developed inside the air passages to approximately 10 psi below the pressure
of the fuel inside the fuel passages (i.e. 80 psi air vs 90 psi fuel). Air exiting the pressure
regulator is discharged through the adaptor plate.
Fuel
Fuel for the engine is stored in a typical fuel tank. A fuel lift pump draws fuel through the
fuel line and fuel filter, then pushes the fuel through a water separating fuel filter. This filter
removes any contaminates and water before the fuel reaches the vapor separator. Fuel
vapors are vented through a hose to the fuel tank. The electric fuel pump in the VST is
different than the fuel pump that is utilized on the standard EFI engine (non DFI), and is
capable of developing fuel pressures in excess of 90 psi. Fuel inside the rail must remain
pressurized at exactly 10 psi over the air rail pressure or the ECM (map) calibrations will
be incorrect. Fuel from the vapor separator is supplied to the top of the port fuel rail. A fuel
line connects the bottom of the first rail to the opposite fuel rail. Fuel is stored inside the
rail until an injector opens. A fuel pressure regulator controls pressure in the fuel rails, and
allows excess fuel to return into the vapor separator. The fuel regulator not only regulates
fuel pressure but also regulates it at approximately 10 p.s.i. higher than whatever the air
rail pressure is. The fuel regulator diaphragm is held closed with a spring that requires 10
p.s.i. to force the diaphragm off the diaphragm seat. The back side of the diaphragm is
exposed to air rail pressure. As the air rail pressure increases, the fuel pressure needed
to open the regulator will equally increase. Example: If there is 50 p.s.i. of air pressure on
the air rail side of the diaphragm, 60 p.s.i. of fuel pressure will be required to open the
regulator. The port fuel rail is water cooled.

DIRECT FUEL INJECTION
Page 3B-19
90-888438 JUNE 2002
To equalize the pulses developed by the pumps (both air and fuel) a tracker diaphragm
is installed in the starboard rail. The tracker diaphragm is positioned between the fuel and
air passages. The tracker diaphragm is a rubber diaphragm which expands and retracts
depending upon which side of the diaphragm senses the pressure increase (pulse).
Oil
Oil in this engine is not mixed with the fuel before entering the combustion chamber. Oil
is stored inside a standard remote oil reservoir. Crankcase pressure will force oil from the
remote oil tank into the oil reservoir on the side of the powerhead. Oil will flow from the
oil reservoir into the oil pump. The oil pump is a solenoid design. It is activated by the ECM
and includes 7 pistons with corresponding discharge ports. The oil pump is mounted di-
rectly onto the powerhead. Each cylinder is lubricated by one of the discharge ports. The
oil is discharged into the crankcase. Bleed hoses carry excess oil from the crankcase to
the transfer ports. The seventh passage connects to the hose that leads to the air com-
pressor for lubrication. Excess oil from the compressor provides lubrication for the upper
and lower crank bearing.
The ECM will change the discharge rate of the oil pump, depending upon engine demand.
The ECM will also pulse the pump on initial start up to fill the oil passages eliminating the
need to bleed the oil system. The ECM provides additional oil for break in, as determined
by its internal clock. The oil ratio varies with engine rpm and load.
Electrical
The electrical system consists of the ECM, crank position sensor (flywheel speed & crank-
shaft position), throttle position sensor (TPS), MAP sensor, engine temperature sensor,
ignition coils and injectors (fuel & direct). The engine requires a battery to start (i.e. the
ignition and injection will not occur if the battery is dead). The system will run off of the
alternator.
Operation
The operation of the system happens in milliseconds (ms); exact timing is critical for en-
gine performance. As the crankshaft rotates, air is drawn into the crankcase through the
throttle shutter, into the plenum and through the reed valves. As the piston nears bottom-
dead-center, air from the crankcase is forced through the transfer system into the cylinder.
As the crankshaft continues to rotate the exhaust and intake ports close. With these ports
closed, fuel can be injected into the cylinder. The ECM will receive a signal from the
throttle position sensor (TPS), engine temperature sensor (TS) and the crank position
sensor (flywheel speed and position sensor). With this information the ECM refers to the
fuel calibration (maps) to determine when to activate (open and close) the injectors and
fire the ignition coils. With the piston in the correct position, the ECM opens the fuel injec-
tor, 90 psi fuel is discharged into a machined cavity inside the air chamber of the air/fuel
rail. This mixes the fuel with the air charge. Next the direct injector will open, discharging
the air/fuel mixture into the combustion chamber. The direct injector directs the mixture
at the bowl located in top of the piston. The piston’s bowl directs the air/fuel mixture into
the center of the combustion chamber. This air fuel mixture is then ignited by the spark
plug.
Compressor Notes: To aid in starting when the air rail pressure is low and before the
compressor has time to build pressure, some direct injectors are held open by the ECM.
This allows the compression from inside the cylinders to pressurize the air rail faster (1
or 2 strokes, or 60°of crankshaft rotation).

DIRECT FUEL INJECTION
Page 3B-20 90-888438 JUNE 2002
Testing Electric Fuel Pump Pressure Output
Low Pressure Electric Fuel Pump
IMPORTANT: After completing fuel pressure tests, reconnect and secure fuel outlet
hose to fuel pump with full circle stainless clamps in Clamp Tool Kit 91-803146A1.
1. Remove outlet fuel hose from low pressure pump. Install a short piece of hose (obtain
locally) onto pump outlet fitting. Install Schrader Valve t-fitting (22-849606) between
outlet fuel hose (removed from pump) and new fuel hose (installed on pump). Secure
hose connections with sta-straps. Due to the low pressure output of this pump, it is
recommended that the air gauge of the Dual Fuel/Air Pressure Gauge
(91-852087A1/A2/A3) be connected to the Schrader Valve. Gauge should indicate
6-9 psi (41.37 - 62.04 kPa).
57416
b
a
c
d
57818
a-Outlet Fuel Hose
b-Low Pressure Electric Fuel Pump
c-Fuel Hose (obtain locally)
d-Schrader Valve (22-849606)