8M2000345 Mercruiser FITTING

All negative battery connections for electronic and electrical components in the electronic control system for marine engines must have a common ground that terminates at the Negative Battery Bus Bar. Improper grounding can cause unreliable and uncontrolled circuit paths. The engine may unexpectedly go to low idle, may fail to shut down, or may fail to change engine speed in response to the control system. Failure of the engine to respond to the control system could result in injury or death. When the electronic control system is installed, modified or repaired, all electronic circuits should be tested for correct installation and operation with the Electronic Control Module (ECM) and the electronic control system before the engine is started.
The alternator, the starting motor and all electrical systems must be grounded to the negative terminal of the battery. The alternator and the starting motor must also meet electrical isolation requirements for marine applications. If the engine has an alternator that is grounded to an engine component, a ground strap must connect the grounded component to the negative terminal of the battery. Also, the component must be electrically isolated from the engine.Negative Battery Terminal Connection
A bus bar is recommended for use as a dedicated common connection to the negative battery terminal for all components that require a negative battery connection. Refer to "Power Supply Connections To The Starting System" in this manual for additional information. This bus bar should be directly connected to the negative battery terminal.Use of the bus bar ensures that the ECM and all connected components have a common reference point. Connected components include switches, sensors, and electronic display modules.Starting System Schematic
Figure 22 - Starting System Schematic for 3126B Marine Engine Abbreviations for Figure 21 - "Starting System Schematic for 3126B Marine Engine":* A "Amp"* ALT "Alternator"* BAT. "Battery"* -BAT. "Negative battery circuit"* -BATTERY BUS BAR "Negative Battery Bus Bar"* +BAT "Positive battery circuit"* +BATTERY BUS BAR "Positive Battery Bus Bar"* +BATTERY (SWITCHED) "Switched Positive Battery circuit"* +BATTERY (UNSWITCHED) "Unswitched Positive Battery circuit"* BK "Black"* BR "Brown"* BU "Blue"* CB "Circuit breaker"* CISS "Customer installed start-stop switch"* CPSS "Customer provided shutdown switch"* GY "Gray"* MTR "Connection for starting motor"* PK "Pink"* PU "Purple"* PWR "Power"* RD "Red"* REMOTE SHUTDOWN INPUT "Shutdown input circuit"* REMOTE START "Remote start circuit"* SM "Starting motor"* SMMS "Starting motor mag switch"* SW "Switch"Power Supply Connections to the Starting System
All negative battery connections for electronic and electrical components in the electronic control system for marine engines must have a common ground that terminates at the Negative Battery Bus Bar. Improper grounding can cause unreliable and uncontrolled circuit paths. The engine may unexpectedly go to low idle, may fail to shut down, or may fail to change speed in response to the control system. Failure of the engine to respond to the control system could result in injury or death. When the electronic control system is installed, modified or repaired, all electronic circuits should be tested for correct installation and operation with the Electronic Control Module (ECM) and the electronic control system before the engine is started.
Table 7: Allowable Wire Length to Connect Starting Motor to the Battery "Allowable Wire Length to Connect Starting Motor to the Battery" gives the size of wire and the maximum allowable length of the wire that is recommended to connect the battery to the starting motor.The size of wire to the positive battery which supplies the power to electrical and electronic components must be of adequate size to carry the maximum current of the circuit.The size of wire to the Negative Battery Bus Bar to which electrical and electronic components have a common connection must be of adequate size to carry the maximum current of the circuit.The causes of intermittent shorts or power interruptions are often very difficult to identify. Proper wire connections for all electrical systems and connection to a common negative bus bar on the vessel are necessary for the correct performance and reliability of the engine.The alternator, the starting motor, and all electrical systems must have a common with the negative battery terminal. The alternator and the starting motor must conform to electrical isolation requirements for marine applications. If the alternator is grounded to an engine component, a ground strap must connect that component to the negative battery terminal. Also, that component must be electrically isolated from the engine.Figure 23 - Minus Battery Connections of Operator Stations for a Two Engine Arrangement All negative battery connections on the components should be directly wired to the Negative Battery Bus Bar. Wire that is a minimum size of 12 AWG should be used to connect the operator stations to the Negative Battery Bus Bar that is located in the engine room.Negative battery connections that conform to Figure 22 "Minus Battery Connections of Operator Stations for a Two Engine Arrangement" ensure that all components in the electrical system have the Negative Battery Bus Bar in the engine room as a common reference point. Reliable operation of the electrical system requires that all of the components in the system are correctly connected.All wires for +Battery and -Battery Bus Bar to the P61 Customer Connector should have a wire size of 14 AWG.Positive Battery Circuit for ECM Power
Do not use fuses for circuit protection. Circuit breakers should be used for circuit protection. Circuit breakers should be located with other circuit protection for the vessel in a dedicated panel that is centrally located.If automatic reset circuit breakers are used, the location of the circuit breaker is critical. The trip point of these circuit breakers can be significantly reduced below the rated trip point if exposed to high temperatures which could cause intermittent shutdowns. Troubleshooting can easily fail to detect this problem which can result in incorrect replacement of components.Use of dedicated circuit protection will reduce the possibility of system performance that is degraded due to voltage transients. Additional electrical loads should not be connected between the ECM and the circuit protection.The ECM Switched Positive Battery terminal keyswitch is connected to Customer Connector