Holley pro-jection 2D Guide

MARINE
2D
Part Number
700-21
For V-8 Engines
INSTALLATION, TUNING, AND
TROUBLESHOOTING MANUAL
NOTE: These instructions must be read and fully understood before beginning
installation. If this manual is not fully understood, installation should not be
attempted. Failure to follow these instructions, including the pictures may result
in subsequent system failure.

TABLE OF CONTENTS:
1.0 INTRODUCTION...................................................................................................................3
2.0 WARNINGS, NOTES, AND NOTICES..................................................................................3
3.0 PARTS IDENTIFICATION.....................................................................................................4
4.0 ADDITIONAL ITEMS REQUIRED FOR INSTALLATION.....................................................6
5.0 TOOLS REQUIRED FOR INSTALLATION...........................................................................6
6.0 SYSTEM OVERVIEW............................................................................................................7
7.0 REMOVAL OF EXISTING FUEL SYSTEM...........................................................................7
8.0 INSTALLATION OF THE MARINE PRO-JECTION FUEL SYSTEM....................................8
8.1 Adapter Plate Installation....................................................................................................8
8.1.1 Square Flange Manifolds..............................................................................................8
8.1.2 Universal and Spread Bore Manifolds...........................................................................9
8.2 Throttle Body Installation ..................................................................................................10
8.3 Throttle Connections.........................................................................................................10
8.4 Fuel Pump Installation......................................................................................................11
8.5 Fuel Pump and Throttle Body Filter..................................................................................11
8.6 Return Line Installation.....................................................................................................12
8.7 Inlet Fuel Line Installation.................................................................................................13
8.7.1 Installation with Fuel Return Line to Fuel Tank...........................................................13
8.7.2 Installation with Fuel Return Line to Electric Pump.....................................................13
8.8 Coolant Temperature Sensor............................................................................................14
9.0 CLOSED LOOP INSTALLATION AND CONNECTION (OPTIONAL):...............................14
10.0 MOUNTING THE ELECTRONIC CONTROL UNIT (ECU):...............................................15
11.0 ENGINE WIRING HARNESS............................................................................................16
12.0 ELECTRICAL CONNECTIONS.........................................................................................17
13.0 FINAL CONNECTIONS.....................................................................................................18
14.0 OPERATIONAL OVERVIEW OF THE DIGITAL ECU ......................................................18
14.1 Main................................................................................................................................19
14.2 Idle..................................................................................................................................19
14.3 High RPM .......................................................................................................................20
14.4 ACCEL Pump .................................................................................................................20
14.5 Choke .............................................................................................................................20
15.0 BEFORE STARTING THE ENGINE..................................................................................20
16.0 SETTING THE MECHANICAL IDLE.................................................................................20
17.0 SETTING THE THROTTLE POSITION SENSOR (TPS)...................................................21
18.0 TUNING THE DIGITAL ECU FOR PERFORMANCE .......................................................22
18.1 Tuning the Main..............................................................................................................22
18.2 Tuning the Idle................................................................................................................22
18.3 Tuning the ACCEL..........................................................................................................23
18.4 Tuning the High RPM .....................................................................................................23
18.5 Tuning the Choke ...........................................................................................................23
19.0 MAINTENANCE AND STORAGE.....................................................................................23
20.0 TROUBLESHOOTING AND COMPONENT TESTING.....................................................24
20.1 Adjusting the Fuel Pressure............................................................................................26
20.2 Testing the Coolant Temperature Sensor.......................................................................26
20.3 Testing the Throttle Position Sensor...............................................................................27
20.4 Testing the Oxygen Sensor (if equipped) .......................................................................28

1.0 INTRODUCTION
Holley Performance Products has written this manual for the installation of the marine PRO-JECTION 2D fuel injection system.
This manual contains all the information needed to install this system. Please read all the WARNINGS, NOTES, and TIPS, as
they contain valuable information that can save you time and money. It is our intent to provide the best possible products for our
customer; products that perform properly and satisfy your expectations. Should you need information or parts assistance,
please contact our technical service department at 1-270-781-9741, Monday through Friday, 7 a.m. to 5 p.m. Central Time. By
using this number, you may obtain any information and/or parts assistance that you may require. Please have the part number
of the product you purchased when you call.
WARNING! The PRO-JECTION 2D system consists of a number of sophisticated components. Failure of any one
component does not constitute, nor does it justify, warranty of the complete system. Individual service
items are available for replacement of components. If assistance is required or if you need further
warranty clarification, you can call Holley Technical Service at the number shown above.
WARNING! To preserve warranty, these instructions must be read and followed thoroughly and completely before
and during installation. It is important that you become familiar with the parts and the installation of the
PRO-JECTION system before you begin. Failure to read and understand these instructions could result
in damage to PRO-JECTION components that are not covered by the warranty and could result in serious
personal injury and property damage.
WARNING! For closed loop systems using an oxygen sensor, use only unleaded fuels with this product. Use of
leaded fuels will destroy the oxygen sensor and will result in incorrect exhaust gas oxygen readings and
improper fuel delivery. Failure to follow these directions does not constitute the right to a warranty
claim.
WARNING! Failure to follow all of the above will result in an improper installation, which may lead to personal injury,
including death, and/or property damage. Improper installation and/or use of this or any Holley product
will void all warranties.
2.0 WARNINGS, NOTES, AND NOTICES
WARNING! For the safety and protection of you and others, only a trained mechanic having adequate marine fuel
system experience must perform the installation, adjustment, and repair. It is particularly important to
remember one of the very basic principles of marine safety: fuel vapors are heavier than air and tend to
collect in lower places. Any fuel spilled will vaporize and remain in the lowest extremes of the engine
compartment of your vessel where an explosive fuel/air mixture may be ignited by any spark or flame
resulting in property damage, personal injury and/or death. Extreme caution must be exercised to
prevent spillage and thus eliminate the formation of such fuel vapors. In all cases, it necessary to have
and properly operate the bilge blower for a length of time sufficient to remove all vapors before starting
your vessel’s engine.
WARNING! United States Coast Guard (U.S.C.G.) regulations apply to vessel equipment specification and operations.
Prior to performing installation, review all pertinent U.S.C.G. rules and regulations.
WARNING! For the safety and protection of persons and property and compliance with all U.S.C.G. and other marine
safety requirements and recommendations, the following instructions must be carefully studied and
applied.
WARNING! Due to the large distance between the helm and the engine in most boats, it is required that the mechanic
have an assistant to operate the helm controls during removal, installation, adjustment, or repair of any
marine fuel system component, as well as during the starting procedure.
WARNING! A U.S.C.G. approved fire extinguisher, in proper operating condition, should be nearby at all times during
removal, installation, adjustment, or repair of the marine fuel system, and during the starting procedure.

3.0 PARTS IDENTIFICATION
ITEM DESCRIPTION QTY SERVICE PART
1 TBI Assembly 700 CFM Complete 1 500-13
2 Electronic Control Unit (ECU) D Systems 1 N/A
3 Wiring Harness 1 534-34
4 Fuel Pump 1 12-927
5 Fuel Pump Clamp 1 N/A
6 Flame Arrestor 1 720-1
7 Manifold Adapter (square flange) 1 17-6
8 Universal Manifold Adapter 1 17-41
9 Universal Manifold Adapter Gasket 1 508-5
10 Square Flange Manifold Adapter Gasket 1 108-10
11 TBI Flange Gasket 1 508-6
12 Coolant Temperature Sensor 1 534-2
13 Oxygen Sensor (optional) 1 43-106
14 Fuel Pump Block-Off Plate 1 12-813
Fuel Pump Block-Off Plate Gasket 1 N/A
15 Throttle Extension Bracket 1 N/A
16 Throttle Extension Bracket Screw and Nut 2 N/A
17 Fuel Filter 1 562-1
18 Fuel Filter Clamp 1 N/A
19 Hose Barb Fitting 3/8 inch 2 N/A
20 Hose Barb Fitting 1/4 inch 1 N/A
21 Brass Tee Connector 1 N/A
22 TBI Mounting Stud 3 N/A
23 Flame Arrestor Mounting Stud 1 N/A
24 Universal Manifold Adapter Screw 8 N/A
25 Nylock Hex Nut (5/16-24) 3 N/A
26 Nylock Hex Nut (1/4"-20) 1 N/A
27 Wire Harness Bracket 1 N/A
28 Cable Ties 12 N/A
29 Hose Clamp 8 N/A
30 Insulated 1/4" Female Quick Disconnect 1 N/A
31 Adapter Plate Plug 3 N/A
32 Pipe Plug 1 N/A
Dielectric Grease (Not Pictured) 1 N/A
Loctite (Not Pictured) 1 N/A
1/4” Marine Fuel Hose (Not Pictured) 4' N/A
5/16" Marine Fuel Hose (Not Pictured) 4' N/A
3/8" Marine Fuel Hose (Not Pictured) 2' N/A
TBI Service Parts:
Fuel Injector 4 522-43
Throttle Position Sensor (TPS) 1 543-3
Item 1 Item 2 Item 3

Item 4 Item 5 Item 6
Item 7 Item 8 Item 9
Item 10 Item 11 Item 12
Item 13 Item 14 Item 15
Item 16 Item 17 Item 18

Item 19 Item 20 Item 21
Item 22 Item 23 Item 24
Item 25 Item 26 Item 27
Item 28 Item 29 Item 30
Item 31 Item 32
4.0 ADDITIONAL ITEMS REQUIRED FOR INSTALLATION
•more 3/8” Marine fuel hose marked U.S.C.G. Type A1 (if needed) •more 5/16” Marine fuel hose marked U.S.C.G.
•5/16” US Coast Guard approved seamless metallic fuel line Type A1 (if needed)
•0-30 psig fuel gauge •Tee fitting for fuel gauge
In addition to the above list, the boat’s engine must be equipped with a four barrel intake manifold, there must be adequate hatch
clearance (1" taller than stock) and the boat’s engine and electrical system must be in good operating condition.
5.0 TOOLS REQUIRED FOR INSTALLATION
•1/2" Socket and Wrench •Small blade standard screwdriver •5/32” Allen wrench
•Medium blade standard screwdriver •#2 Phillips screwdriver •Digital Volt-Ohm meter
•Drill and assorted bit sizes •Hole saw (2”) •Terminal crimping tool
•Engine tachometer •Torque wrench •Utility knife
•12 volt test light
An assistant is necessary for some installation and adjustment procedures and should be present for safety reasons. If you
don't have a test light, we would suggest that you purchase one for use in this installation.

6.0 SYSTEM OVERVIEW
The projection system actually consists of three systems; the air and fuel delivery, the fuel return system, and the electronic
control system. Because the ECU utilizes digital electronics, it is not affected by variations in temperature or humidity.
Although the digital ECU is pre-programmed at the factory, the amount of fuel delivered to the engine under various operating
conditions is user-adjustable through the use of five adjustments knobs located on the front panel of the digital ECU. These
adjustment knobs are used to tune the system. The Digital ECU has adjustments for Choke, Acceleration, Idle, Main, and High
RPM settings. By simply dialing in the appropriate fuel curve, fuel delivery can be accurately matched to the engine’s
requirements across its entire power band.
The fuel is pumped from the tank to the Pro-Jection throttle body through the fuel filter. At the rear of the throttle body is the fuel
pressure regulator, which maintains the fuel pressure at 15 psi (or any pressure you choose between 12 and 22 psi). Excess
fuel not injected into the engine is returned to the fuel tank via the fuel return line.
The ECU is factory programmed and controls the amount of fuel delivered to the engine by pulsing each of the two fuel injectors
for precisely controlled periods of time. The rate and length of time at which the injectors are pulsed is calculated from various
inputs such as engine speed, throttle position, engine coolant temperature, and an optional oxygen sensor. Below is a
Projection system layout of all three systems.
WARNING! The Digital Pro-Jection system is NOT recommended for high-speed, high-performance engine
applications.
Figure 1
NOTE: Although every possible precaution was taken in the design of the digital ECU to prevent interference from radio
sources, the use of solid core spark plug wires may interfere with the operation of the ECU. Holley recommends the
use of either suppression or spiral wound spark plug wires, such as Holley Part #’s 50-9800, 50-9801, or 50-9804.
7.0 REMOVAL OF EXISTING FUEL SYSTEM
1. Disconnect the battery and remove the flame arrestor.
2. Before disconnecting any vacuum hoses, it is a good idea to sketch out the vacuum hose routing. Using masking tape and
a permanent marker, mark all the vacuum hoses, vacuum sources and ports before removing the old fuel delivery system.
3. Remove and discard the fuel line that connects the fuel delivery system to the fuel pump. This will not be needed in the
installation.

4. Disconnect and plug the inlet fuel line that runs from the gas tank to the fuel pump. This will prevent fuel spillage and
foreign matter or dirt from entering the fuel line.
DANGER! BEFORE DISCONNECTING OR REMOVING FUEL LINES, ENSURE THE ENGINE IS COLD. DO NOT SMOKE.
EXTINGUISH ALL OPEN FLAMES. AN OPEN FLAME, SPARK, OR EXTREME HEAT NEAR GASOLINE CAN
RESULT IN A FIRE OR EXPLOSION CAUSING PROPERTY DAMAGE, SERIOUS INJURY, AND/OR DEATH.
5. The fuel delivery system can now be removed. Holley recommends removing the mechanical fuel pump, if so equipped,
and blocking-off the fuel pump mount using the provided fuel pump block off plate. The PRO-JECTION system kit includes
a block-off plate that will fit small and big block Chevrolet and Chrysler engines. If the block-off plate does not fit your
engine, a block-off plate may have to be purchased from a local performance parts supplier.
6. If required, replace the intake manifold at this time. Proceed to step seven if this is not required. A 4-BARREL STOCK OR
AFTERMARKET INTAKE MANIFOLD IS REQUIRED FOR THE INSTALLATION OF THE HOLLEY DIGITAL PRO-
JECTION.
7. Place clean shop towels or rags into the manifold opening to prevent dirt or debris from entering the engine. Keep exposed
ends of vacuum and fuel lines free from dirt.
WARNING! Failure to cover the intake opening with a clean towel could result in dirt or debris entering the engine.
Dirt or debris in the induction system can cause engine damage, which may necessitate a complete
engine overhaul.
8. Remove all traces of the old gasket material from the TBI mounting flange. DO NOT gouge the intake manifold sealing
surface during removal of old gasket material. Failure to remove all traces of old gasket material will result in vacuum leaks
that will be difficult to detect later. Sealing flanges must be clean and dry before installation.
9. Remove the shop towels from the intake and vacuum out the intake channel to ensure no dirt or debris is left in the intake
system. Place shop towel over the entire intake opening until you are ready to install the new PRO-JECTION TBI.
8.0 INSTALLATION OF THE MARINE PRO-JECTION FUEL SYSTEM
8.1 Adapter Plate Installation
Determine which type of mounting flange you have on your intake manifold. A square flange accepts a standard Holley
carburetor or universal, and a spread bore flange accepts a Rochester Quadra-Jet carburetor. Make sure the gasket surface on
the mounting flange is clean and any old gasket material has been removed. After determining the mounting flange
requirements, find the appropriate installation listed below.
8.1.1 Square Flange Manifolds
1. Using Figure 2 as your guide, place the square-holed gasket and then the manifold adapter on the manifold. The square
opening of the adapter should be facing downward and the wide opening should be facing upward toward the FRONT of the
engine.
2. Check to ensure that the gasket lies flat and adequately covers all surfaces.
3. Put the gasket and then the adapter over the manifold adapter. Position the bores, so they are placed forward toward the
primary bores of the manifold.
4. Insert the four 1-3/4" adapter bolts through the outer holes of the adapters and gaskets and into the manifold. Torque the
bolts to 15 ft./lbs. in two steps. First, torque each to 8 ft./lbs., and then to 15 ft./lbs. in a criss-cross pattern.

Figure 2 Figure 3
8.1.2 Universal and Spread Bore Manifolds
WARNING! If using an aftermarket manifold on a Chevrolet small block, position the adapter bores so they are forward
toward the front of the manifold. On all other applications with any type of manifold, stock or aftermarket,
position the adapter bores so they are forward toward the front or primary bores of the manifold. On
factory big block Chevrolet manifolds, the throttle body must be mounted forward even though the bores
don't line up properly. This must be done to prevent the front cylinders from running lean.
1. Using Figure 3 as your guide, put the gasket and then the adapter on the manifold.
NOTE: On a small block Chevrolet application with stock intake manifold, position the adapter so the bores are over the large
secondary bores in the manifold.
2. Check to ensure that the gasket lays flat and adequately covers the sealing surface.
3. Insert the four 1-1/4" adapter bolts through the inner holes of the adapter and gasket and into the manifold. Torque the bolts
to 15 ft./lbs. in two steps. First, torque each to 8 ft./lbs. and then to 15 ft./lbs. in a criss-cross pattern.
NOTE: Some applications originally equipped with a Quadra-Jet carburetor may require the use of Holley’s throttle cable
bracket P/N 717-6.
NOTE: Mercruiser applications will require the throttle cable bracket P/N 717-6 and Holley's linkage adapter P/N 717-7. Install
the bracket along with the proper gaskets between the manifold and the adapter plate.
NOTE: Throttle extension bracket must also be used when the TBI is mounted over the secondary bores on stock small block
Chevrolet manifolds. Mount this to the 717-6 bracket using the two nuts and bolts that are provided.
WARNING! The universal manifold adapter has six-threaded TBI mounting holes and only three of these will be used
to mount the TBI. Plug the remaining holes by applying a couple drops of Loctite to each plug and insert
into the unused holes. Use a 5/32 hex wrench and screw each plug in until the sit below the adapter plate
surface.

8.2 Throttle Body Installation
NOTE: Remove and discard the special shipping bolt as shown in Figure 4. Apply a couple drops of Loctite to the long end of
the flame arrestor stud and insert into the throttle body and tighten securely. After the flame arrestor is installed it is
EXTREMELY IMPORTANT that the flame arrestor stud does not extend any farther than 1/2 inch past the top cover of
the flame arrestor, damage to the engine cover or hatch may result. Trimming may be necessary.
Figure 4
1. Locate the three 5/16" studs and screw the coarse thread ends into the proper TBI adapter mounting holes.
2. Place the gasket and throttle body over the studs and tighten with locking nuts to 15 ft./lbs. in two steps. First, torque each
to 8 ft./lbs. and then to 15 ft. /lbs. in a criss-cross pattern.
8.3 Throttle Connections
NOTE: Some applications originally equipped with a Quadra-Jet carburetor may require the use of Holley’s throttle cable
bracket P/N 717-6.
NOTE: Mercruiser applications will require the throttle cable bracket P/N 717-6 and Holley's linkage adapter P/N 717-7. Install
the bracket along with the proper gaskets between the manifold and the adapter plate.
NOTE: Throttle extension bracket must also be used when the TBI is mounted over the secondary bores on stock small block
Chevrolet manifolds. Mount this to the 717-6 bracket using the two nuts and bolts that are provided. Or when the old
throttle lever arm is significantly longer then the Pro-Jection throttle lever arm. See step 2.
1. Remove any studs or brackets that are on the carburetor throttle lever and transfer them over to the lever of the TBI in the
same relative location. Connect the throttle cable to the lever using the original equipment hardware. If Using the Holley
717-6 and/or 717-7 throttle linkage kits. Follow the instructions that come with these kits. In some cases it will require the
use of the throttle lever extension brackets. Step two outlines the procedure for using the throttle lever extension bracket.
2. Measure the length of the throttle lever arm on the carburetor removed from the boat. Compare the length of the existing
throttle lever arm with the one on the PRO-JECTION throttle body. If the two throttle lever arms are similar in length (within
1/2” of each other), the throttle lever arm hole on the PRO-JECTION throttle body can be used without the extension
bracket. Use the throttle lever arm extension bracket if the old throttle lever arm is significantly longer than the PRO-
JECTION throttle lever arm. Before installation of the bracket, check the diameter of the throttle cable stud. Some Systems
may use a 1/4” stud that will require drilling of the appropriate hole in the extension bracket to a 1/4” diameter. Attach the
extension bracket using two fillister head screws. The extension lever length can be adjusted using the four sets of holes.
3. Attach throttle linkage and have an assistant get in the boat and fully actuate the throttle controls. Make the necessary
adjustments to the throttle linkage to ensure that the throttle plates are vertical when the throttle control is wide open. Work
throttle linkage back and forth several times to ensure it operates smoothly with no binding or sticking.

DANGER! STICKING THROTTLE MAY RESULT IN UNCONTROLLED ENGINE OR BOAT SPEED. THIS COULD CAUSE
PROPERTY DAMAGE, PERSONAL INJURY, OR DEATH. A STICKING THROTTLE MAY BE CAUSED BY
IMPROPERLY INSTALLED THROTTLE CABLES, LACK OF CLEARANCE FOR ANY OF THE THROTTLE
LINKAGE, OR BY BINDING THROTTLE LINKAGE. CHECK ALL THROTTLE CABLES FOR PROPER
INSTALLATION AND ALIGNMENT AND ACTUATE THE THROTTLE TO CHECK FOR ANY POTENTIAL
BINDING OR CLEARANCE PROBLEMS AND REPAIR ANY PROBLEMS.
NOTE: Ensure that the factory shift interrupt (if equipped) has been properly reconnected, is in proper working order, and does
not cause any throttle actuation problems.
8.4 Fuel Pump Installation
1. Install one end of the brass T-fitting onto the threaded adapter fitting that is on the pump. Be sure to use a small amount of
pipe thread sealer on the threads and also use two wrenches when tightening the fittings so no force is applied to the pump
body.
2. Install a 3/8" hose fitting in the other end of the T-fitting.
3. Install the 1/4" barbed hose fitting or the pipe plug into the middle opening of the T-fitting. Use the hose fitting if routing the
return line to the inlet of the pump. Use the plug if routing the return line back to the tank. See the return line installation
section for explanation of return line options.
4. Pursuant to Coast Guard regulations, the electric fuel pump must be mounted directly to the engine or within 12” of the
engine. In addition, the pump should be mounted as low as possible to prevent excessive noise and potential vapor
lock problems. Install the small cushioned clamp around the center portion of the pump body. Mount the pump and clamp
assembly onto the engine or within 12” of the engine using the hole provided in the clamp.
Figure 5
DANGER! TAKE PRECAUTIONS TO ENSURE THAT ALL FUEL LINE ROUTINGS ARE AWAY FROM HEAT SOURCES,
SUCH AS THE ENGINE OR EXHAUST SYSTEM. FAILURE TO DO SO COULD RESULT IN A FIRE OR
EXPLOSION HAZARD AND CAUSE PROPERTY DAMAGE, SERIOUS INJURY, AND/OR DEATH.
WARNING! Marine fuel systems use an anti-siphon valve. A factory carburetor anti-siphon valve may not work
properly with a PRO-JECTION fuel system. The user may experience high levels of noise and/or vapor
lock problems due to the anti-siphon valve being too restrictive. The anti-siphon valve should be replaced
with a high flow capacity valve.
8.5 Fuel Pump and Throttle Body Filter
1. The fuel filter should be plumbed in between the electric pump outlet and the inlet fitting of the TBI. Install the large
cushioned clamp around the center of the filter. Position the filter so the fuel hoses can be routed without kinks or sharp
bends.

2. Start by cutting two sections of 3/8" fuel hose. One piece goes form the pump outlet to the filter and the other from the filter of
the TBI inlet. Be sure the arrow on the filter indicating flow direction.
3. Push the hoses onto the filter all the way until they contact the filter body. Secure the hoses with clamps.
4. Connect the free ends of the hoses to the TBI inlet and the Pump outlet and secure with hose clamps.
5. Conveniently mount the filter using the fuel filter clamp.
6. Use the existing boat fuel filter or a OMCfilter kit part number 174176 or equivalent. The purpose of this filter is to protect
the fuel pump from particles of dirt or other foreign material. The filter should be installed with the arrow on the filter pointing
in the direction of the fuel flow. Secure the ends of the fuel lines with U.S.C.G. approved hose clamps.
8.6 Return Line Installation
The Holley digital PRO-JECTION System requires a return fuel line to the fuel tank so that unused fuel can be routed from the
throttle body. There are two methods of installing a return line on a boat. The preferred method is to run a hose or line from the
throttle body outlet back to the fuel tank. This can be done only if the return line fittings are already on the fuel tank. If a return
line does not currently exist on the boat, the user may want to remove the fuel tank and modify it with an additional fitting of 1/4”
I.D. minimum. The tank should be cleaned if removed and modified. The other method is used when there is no access to the
tank. The return line must then be routed from the throttle body outlet back to the inlet side of the electric fuel pump. A
minimum size of 1/4” I.D. is recommended for the return fuel line. Determine if the fuel system return lines will be routed using a
return to the fuel tank system, or a return to the inlet side of fuel pump system. See Figure 6 for a diagram of the two fuel
system configurations. Once a determination has been made, go to the section below required for your installation and follow
the installation steps.
DANGER! ALL FUEL LINES MUST BE U.S.C.G. APPROVED. METALLIC LINES MUST BE MADE OF SEAMLESS
ANNEALED COPPER, STAINLESS STEEL, NICKEL COPPER, OR COPPER NICKEL AND EXCEPT FOR
CORRUGATED FLEXIBLE LINE, HAVE A MINIMUM WALL THICKNESS OF .029 INCHES. RUBBER HOSE
MUST BE MARKED “U.S.C.G. TYPE A1”. UNITED STATES COAST GUARD APPROVED HOSE CLAMPS
MUST ALSO BE USED. USE OF AUTOMOTIVE GRADE FUEL LINES COULD CAUSE A FIRE OR EXPLOSION
HAZARD WHICH COULD CAUSE PROPERTY DAMAGE, SERIOUS INJURY, AND/OR DEATH.
WARNING! Use only approved fuel lines. Follow all U.S.C.G. rules and regulations. The return fuel line should enter
the fuel tank at the “fuel level sending unit flange” or at the “filler neck”. The filler neck or sending unit
must be removed from the tank to perform this operation.
DANGER! PROPER INSTALLATION OF THE FUEL RETURN LINE MAY NECESSITATE COMPLETE REMOVAL OF THE
FUEL TANK. THIS WORK SHOULD BE DONE BY A FUEL TANK SPECIALIST, WHO HAS BEEN TRAINED IN
THIS WORK AND IS FAMILIAR WITH SAFETY REGULATIONS AND PRECAUTIONS NECESSARY TO DO
THIS WORK. IF A PERSON ATTEMPTS THIS WORK WHO IS NOT FAMILIAR WITH THE SAFETY
REGULATIONS AND PRECAUTIONS, AN EXPLOSION HAZARD MAY RESULT IN PROPERTY DAMAGE,
SERIOUS INJURY, AND/OR DEATH.
NOTE: Anchor all fuel lines securely at 1-½ foot intervals. The use of U.S.C.G. approved fuel line tubing will afford maximum
fuel line protection against premature wearing due to flexing, temperature extremes, salt water, weather, etc.
Attach a section of 5/16" hose to the outlet of the throttle body and secure with a hose clamp. Run the other end to either the
fuel tank (Method 1) or the inlet of the pump at the T-fitting as previously discussed in earlier text (Method 2). Secure with
clamps.
NOTE: 1/4” U.S.C.G. approved hose is included with the kit, should it be required for specific applications.

Figure 6
8.7 Inlet Fuel Line Installation
8.7.1 Installation with Fuel Return Line to Fuel Tank
The mechanical pump should not be used when the fuel return line goes to the fuel tank. Route a section of 3/8” hose from the
boat fuel tank and fuel filter to the barbed fitting on the inlet of the PRO-JECTION electric fuel pump. Secure with clamps at
each end of the hose. The stock pump should be removed and replaced with a block-off plate. Plug the fume tube in the throttle
body.
8.7.2 Installation with Fuel Return Line to Electric Pump
Holley recommends that the mechanical pump be removed in this case. However, the pump can be optionally retained if the
user wants to supply the electric pump with the mechanical pump. Install the 3/8” hose from the boat fuel tank and fuel filter to
the 3/8” hose barb on the tee fitting. Then install the 3/8” hose from the tee fitting to the inlet of the PRO-JECTION electric fuel
pump. Secure with clamps. Install the vent hose from the mechanical fuel pump (if equipped) to the fuel fume tube on the TBI.
WARNING! Be sure that there is a fuel filter between the fuel tank and pump(s). If one must be added, use an OMC
filter kit number 174176 or equivalent.

8.8 Coolant Temperature Sensor
Install the temperature sensor in a water passage of the intake manifold. Most intake manifolds have a plug that can be
removed for installation of a temperature sensor. In addition, some cylinder heads have a plug that can be removed for
installation of a temperature sensor. DO NOT install the sensor in the thermostat housing. The sensor must be located so that it
is in contact with coolant on the lower side of the thermostat. If a location cannot be found, a metal tee fitting may be installed at
the boat’s temperature gauge sensor, if so equipped. Then the gauge and PRO-JECTION temperature sensor can be installed
into the tee fitting. DO NOT use any pipe sealer on the threads that may degrade or reduce the ground connection of the
sensor. Tighten the sensor to 15 ft./lbs. torque.
9.0 CLOSED LOOP INSTALLATION AND CONNECTION (OPTIONAL):
The digital ECU is designed to utilize a heated, three-wire oxygen sensor to operate the system in a closed loop mode. When
operating in a closed loop mode, the electronic control ECU utilizes a reference signal from the oxygen sensor to determine
whether the engine is running too rich or too lean. The ECU then adjusts the fuel delivery to maintain a stoichiometric fuel
delivery (14.7:1 Air / Fuel Ratio).
NOTE: The installation of an oxygen sensor will operate with the digital ECU. This requires use of the Holley Digital PRO-
JECTION 2D Closed Loop Kit for 1 and 2-Barrel Applications, P/N 534-54.
WARNING: If you are currently using a Holley analog closed loop kit, P/N 534-27, all electrical wiring connecting to
this kit must be removed and replaced with a new wiring harness, Holley P/N 534-56. Failure to replace
this wiring harness will result in improper fuel delivery and possible damage to ECU.
WARNING! Use only unleaded fuels when operating an oxygen sensor. Use of Leaded fuels will DESTROY the
oxygen sensor and will result in incorrect exhaust gas oxygen readings, which may cause poor
performance and cause serious engine damage.
WARNING! The use of some RTV Silicone sealant will destroy the oxygen sensor. Ensure that the RTV silicone
sealant that you use is compatible with oxygen sensor vehicles. To determine compatibility, check the
packaging of your RTV silicone or contact the sealant manufacturer.
WARNING! An experienced inboard mechanic should be used for installation of the oxygen sensor. Inboard engine
exhaust manifolds have water passages inside them for noise and cooling purposes. An improperly
drilled manifold will result in water getting into the oxygen sensor causing it to be destroyed and
destroying the exhaust manifold. The oxygen sensor should be installed as far from a water location as
possible and as close to an exhaust port as possible.
NOTE: The oxygen sensor, if used, should be installed by someone with experience with inboard boat engine exhaust systems.
Any competent inboard repair shop should be able to perform this task at a minimum cost.
Locate a position for the oxygen sensor as close to the engine as possible. Pick a location that allows easy installation and
removal of the oxygen sensor. Figures 7 & 8 show the location used by Holley engineers during development of the Marine
PRO-JECTION systems. The oxygen sensor was mounted in the exhaust port farthest from the water injection hose and riser
tube at the top of the picture. This location was chosen to prevent water that is pumped into the exhaust system from running
back down the riser tube and into the exhaust manifold. This can wet the oxygen sensor and cause damage to the oxygen
sensor. The close-up shows that the hole for the oxygen sensor was drilled through an area of the manifold that does not have
any water passages. This should be done to prevent any possibility of water leakage from the wet areas of the manifold to the
dry areas.

Figure 7
Figure 8
1. If the oxygen sensor is being installed directly into the exhaust manifold, the manifold will have to be drilled and tapped for
the oxygen sensor threads. The location for the oxygen sensor should be chosen very carefully. The sensor must be
located in an area that can be drilled without passing through any of the manifold water jackets. The oxygen sensor must
be kept dry for proper operation and should not pass through any water passages to prevent any water leakage. Drill a hole
in the location picked for the sensor using a 5/8 inch drill size.
2. Tap the hole using a m18 x 1.5-5H metric tap.
3. Install the oxygen sensor into the threaded hole and tighten securely. Care should be taken not to over tighten the sensor
when aluminum manifolds have been used. It is a good idea to add anti-seize to the threads to aid if oxygen sensor
removal is necessary.
10.0 MOUNTING THE ELECTRONIC CONTROL UNIT (ECU):
DANGER! ALWAYS DISCONNECT YOUR BOATS BATTERY BEFORE PERFORMING ANY WORK ON THE ELECTRICAL
OR FUEL SYSTEM. FAILURE TO DO SO MAY PRODUCE SPARKS, CAUSING A FIRE OR EXPLOSION,
RESULTING IN PROPERTY DAMAGE, PERSONAL INJURY, AND/OR DEATH.
WARNING! Do not open the ECU. The digital electronics contained within this ECU are sensitive to static electricity.
Opening this ECU WILL VOID THE WARRANTY.

WARNING! Do not mount the ECU in an enclosed area. Mount the ECU in an area that will allow air to flow freely
across the ECU to dissipate heat generated by the ECU.
WARNING! When mounting the ECU, care must be taken that none of your boats other systems, such as the electrical
system, are damaged by either drilling holes or using mounting screws. Always check on the other side
of the location that is to be drilled to ensure that no damage will occur.
WARNING! Do NOT mount the ECU in the engine compartment. The ECU is not designed for the environment (heat,
moisture) present in the engine compartment. Premature failure of the ECU will result.
WARNING! The PRO-JECTION 2D system must be appropriately grounded to ensure proper system performance and
to prevent any damage to the system.
NOTE: All connections shown MUST be made in order for the PRO-JECTION 2D system to operate properly.
1. Pick a suitable location on the interior of the boat in which the ECU can be mounted. Ensure the mounting location allows
for sufficient length of the wiring harness and clearance for connectors and the adjustment knobs on the front of the ECU
are accessible before mounting the ECU.
2. Using the ECU base plate as a template, drill 4 pilot holes, ensuring that no damage will result to any of your boats other
systems.
3. Mount the ECU with 4 self-starting sheet metal screws (not included).
11.0 ENGINE WIRING HARNESS
1. At a location near the ECU mounting, pick a suitable location on the engine compartment bulkhead for the wiring harness to
pass through. A 2” diameter hole will be required for the wiring harness. Check both sides of the bulkhead for interference.
WARNING! Before drilling, check both sides of the bulkhead for possible interference with electrical systems, etc.
Failure to do so can result in damage to one of the boat systems.
2. Use a 2” hole saw (available at any hardware store) or a punch out tool to cut through the bulkhead, as necessary.
3. Feed the wiring harness from the location of the ECU to the engine compartment. Check to ensure sufficient length of
harness is available for attaching to the ECU.
4. Slit a 2” grommet and position around the wiring harness. Slip the grommet into the 2” hole to prevent the wiring harness
from chaffing. A light application of WD-40 on the grommet will ease the installation.
5. Connect the wiring harness to the ECU. Push the plug into the ECU until the lock snaps into position.
Figure 9

12.0 ELECTRICAL CONNECTIONS
The cable assembly plugs into the ECU and also connects to the throttle body, fuel pump, sensors, electrical power, and ground.
Apply a small amount of dielectric grease to all electrical terminals and connections.
WARNING! Keep all wires away from hot or moving parts as much as possible. Your kit includes cable ties to secure
wires clear. Bare or frayed wires can result in electrical short circuits, which can cause system failure.
Start with the bundle containing the three-way male connector and the black and brown wires. See Figure 9. Plug the three-way
connector with the grey, blue and black wires into the throttle position sensor on the TBI until it locks in place. The black wire
with the ring terminal must be secured to an engine block or intake manifold bolt. Be sure the connection is free from rust dirt or
paint. Next connect the brown wire to the temperature sensor. The pink wire must go to ground. The voltage on this terminal
must be zero when the engine is off or running.
NOTE: Good grounding is essential to make this system operate correctly.
The other bundle in the harness contains the four-way connector with two red wires, a violet wire, and a orange wire. Plug this
four-way connector and push this into the fuel pump until it is secure. The single black wire with a ring terminal is the ground.
Bolt this to the engine just as you did with the previous black wire. The white wire with the ring terminal is the tach signal input
to the ECU. This wire is usually connected to the (-) side of the ignition coil. If hooking up to a GM HEI ignition, a 1/4" female
terminal will have to be used in place of the ring terminal before connecting to the tack output on the distributor cap. If an
aftermarket ignition is used and has a jack labeled "tach signal" or similar, connect the white wire to this point. The last wire to
connect is the red wire with the fuse holder. This is the main power lead for the system and must be wired to a source that is
energized during the on and crank positions of the ignition switch. Reconnect the battery momentarily and use a voltmeter to
find this. Be sure to disconnect the battery after a suitable power source is located. The harness is designed to directly hook up
to the IGN terminal of a GM HEI distributor. See Figure 10. For other types of ignition systems, power must be found
elsewhere. In this case, trim the fuse holder cable as shown in Figure 11. In some cases, a wire must be run from the boat
ignition switch back to the fuse holder on the harness. Use 14 gauge wire or larger if this is done.
Figure 10
Figure 11

WARNING! For proper operation, the voltage on the fuse holder wire should be 12-15 volts while the engine is running
and should remain above 8.5 volts while the engine is being started. Low voltage will result in poor
operation or an inoperative system. Double check the voltage after the installation is complete.
WARNING! The use of solid core ignition wires may adversely affect the function of the electronic control unit. We
recommend the use of suppression or spiral core wires.
NOTE: Alternator output voltage is critical with the Pro-Jection system. If the alternator is not supplying specification output
(about 14 volts) when the engine is running, repair the system so it does supply the correct voltage.
13.0 FINAL CONNECTIONS
Plug the white 12-pin connector into the ECU. Install the harness bracket onto the ECU to hold the connector in place. To do
so, remove the two lower cover screws, install the bracket, and replace the screws.
Shown in Figure 12 is the proper installation of the distribution ring on the throttle body. Be sure the tabs point upward and rest
along the injector pods. The injector pod screw closest to the TPS switch must be removed and reinstalled to hold the
distribution ring in place.
WARNING! It is important for the distribution ring to be properly installed and retained. Failure to do so will cause
inadequate seal between the throttle body and flame arrestor and may be a fire hazard in the event of a
backfire.
Figure 12
14.0 OPERATIONAL OVERVIEW OF THE DIGITAL ECU
This digital ECU is programmed at the factory with fuel maps. The ECU utilizes inputs from various sensors and from the
adjustment knobs located on the front of the ECU to calculate the appropriate fuel delivery to the engine.
When the ignition switch is in the "On" position, battery power is applied to the red wire of the ECU, fuel pump (+) terminal and
one side of each injector coil. Upon initial power up, the fuel pump will run for a couple of seconds to help prime the fuel lines.
The ECU controls the pump by grounding the green wire going to the (-) terminal of the pump. As the engine is being started,
battery power is applied to the pink wire, which enables the ECU to operate the fuel pump, and pulses the injectors, so fuel is
delivered into the throttle body. After the engine starts up and the ignition switch is released from the crank position, the ECU
relies on tach signals from the white wire to operate the pump and injectors to run the engine. If for some reason the engine
stalls, this is most likely due to the absence of tach signals, which causes the ECU to shut off the injectors and the fuel pump.
The temperature sensor is designed to have a high resistance when cold (about 10K ohms at 20°F) and a low resistance when
warm (about 200 ohms at 200°F). This sensor tells the ECU to deliver a richer fuel mixture during cold engine operation and
gradually leans out at the engine warms up. The brown wire can be grounded to disable the choke function. This may be
required if the coolant temperature is less than 150 when the engine is fully warmed up.
The throttle position sensor (TPS) tells the ECU how far and how fast the throttle is opened. The ECU sends a 5 volt reference
signal to the TPS along the gray wire and the voltage on the blue wire varies depending on how far the throttle is opened. A low
voltage appears at idle with the voltage increasing as the throttle is moved to open. A “CLEAR FLOOD” mode has also been
programmed into the ECU to aid in vehicle startup in case excessive fuel has entered the intake manifold. Should the engine
flood during start up, the clear flood mode can be initialized by turning the ignition off, opening the throttles fully and cranking the
engine until it starts. There is also a back-up mode, which allows the boat to be driven in the event of TPS failure. If the TPS

19
should "open circuit", causing a lean condition, the back up automatically takes place. If the TPS "short circuits", causing a rich
condition, you must remove the wire harness connector from the TPS. The idle will be richer and top speed will be limited in this
mode. DO NOT operate for an extended period of time in this mode.
WARNING! The throttle position sensor may become damaged if exposed directly to liquid. Protect the TPS when
washing the engine.
The oxygen sensor provides information on whether the engine is running rich or lean. Even though the oxygen sensor is
heated, the ECU will continue to operate in an open loop mode for a short period of time after initial start-up. This combined
information is then used by the ECU to adjust the fuel delivery to the engine.
In addition to the information provided to the ECU by the various sensors, the user is also able to adjust the fuel delivery through
the use of the five adjustment knobs on the front of the ECU. The user is able to adjust fuel delivery for Choke, Accelerator
Pump, Idle, Main, and High RPM settings. A detailed description of each adjustment is given below. Refer to Figure 13 during
the discussion of each of the adjustments.
The fuel map that is programmed into the digital ECU is comprised of 256 individual points. Each point has a throttle position
and rpm value assigned to it. These values are used by the digital ECU to determine the appropriate fuel delivery when the
system is in operation
Fuel Map Areas of Adjustment
Figure 13
14.1 Main
The MAIN adjustment knob allows the user to adjust the fuel delivery of the entire fuel map 50% above or below the values set
at the factory. Rotating the knob clockwise will raise the fuel map vertically, therefore increasing the fuel delivery for all points in
the map. Rotating the knob counter-clockwise will lower the map vertically, therefore decreasing the fuel delivery for all points in
the map.
NOTE: In tuning the system, the MAIN is the first value to be adjusted. All other adjustments are made AFTER the MAIN has
been properly set.
14.2 Idle
The Idle adjustment knob allows the user to adjust the fuel delivery in the idle region of the fuel map 30% above or below the
values that are set at the factory. This is accomplished by moving the lower part of the fuel map either up or down along a
hinged horizontal line as indicated in Figure 13. Adjustments to the idle region of the fuel map are made AFTER the MAIN
Adjustment knob has been properly adjusted. Turning the knob clockwise increases the fuel delivery, while a counter-clockwise
rotation decreases the amount of fuel delivered to the engine during idle.

14.3 High RPM
The HIGH RPM adjustment knob allows the user to adjust the fuel delivery for engine speeds over 3000 rpm 50% above or
below the values that are set at the factory. This is accomplished by moving the fuel map either up or down along a diagonal
hinged line as indicated in Figure 13. Turning the adjustment knob clockwise increases the fuel delivery, while a counter-
clockwise rotation decreases the amount of fuel delivered to the engine at high engine speeds.
14.4 ACCEL Pump
The ACCEL PUMP adjustment knob allows the user to adjust the addition of fuel for acceleration 50% above or below the value
set at the factory. Rotating the adjustment knob clockwise results in additional fuel being added to the fuel enrichment set at the
factory, while rotating the adjustment knob counter-clockwise will result in less fuel being added during acceleration. The proper
adjustment is made while performing acceleration tests, which are described later on in this section.
14.5 Choke
The CHOKE adjustment knob allows the user to adjust the amount of fuel enrichment while the engine is warming up 20% above
or below the value set at the factory. Rotating the adjustment knob clockwise will increase the amount of fuel added while the
engine is warming up. Rotating the adjustment knob counter-clockwise will decrease the amount of fuel added while the engine
is warming up.
15.0 BEFORE STARTING THE ENGINE
WARNING! The adjustment knobs on the front of the ECU are precision manufactured parts and do not require a great
deal of force to turn. Do not apply excessive force to the adjustment knobs. Full adjustment range for the
knobs is 3/4 of a turn.
Figure 14
1. After all electrical connections have been made, double-check all connections to ensure that they are tight and secure.
2. Reconnect the battery.
3. If installed, remove the oxygen sensor harness from the digital ECU by unplugging the harness from the rear of the ECU.
4. Although the adjustment potentiometers on the front of the digital ECU were set at the factory in the null position, check to
ensure that they were not moved. If necessary, rotate the potentiometers, so that they are positioned as in Figure 14.
5. Turn the ignition key to the “RUN” position. DO NOT START THE ENGINE. Listen for the fuel pump. The fuel pump
should run for several seconds before shutting off.
6. Turn the ignition key to the “OFF” position.
16.0 SETTING THE MECHANICAL IDLE
The setting of the mechanical idle speed is critical in the operation of the Digital ECU and is best accomplished by using a
tachometer. If your vehicle is not equipped with a tachometer, Holley highly recommends one be used. To adjust, follow the
instructions carefully.