NUT 5C7261 - Caterpillar

Electrical shock hazard. The electronic unit injector system uses 90-120 volts.
The ECM sends a high voltage signal to the unit injectors. To help prevent personal injury, do not disconnect the unit injector connector while the engine is operating. Do not come in contact with the harness connector for the unit injector while the engine is operating.Never disconnect any charging unit circuit or battery circuit cable from the battery when the charging unit is operating. A spark can cause the combustible gases that are produced by some batteries to ignite.To help prevent sparks from igniting combustible gases that are produced by some batteries, the negative "−" jump start cable should be connected last from the external power source to the negative "−" terminal of the starting motor. If the starting motor is not equipped with a negative "−" terminal, connect the jump start cable to the engine block. Check the electrical wires daily for wires that are loose or frayed. Tighten all loose electrical wires before the engine is operated. Repair all frayed electrical wires before the engine is started. See this Operation and Maintenance Manual, "Starting the Engine and Cold Weather Starting" for specific starting instructions.Grounding Practices
The electrical system for the vessel and the engine must be properly grounded. Proper grounding is necessary for optimum engine performance and reliability. Improper grounding will result in uncontrolled electrical circuit paths and in unreliable electrical circuit paths.Uncontrolled electrical circuit paths can result in damage to main bearings, to crankshaft bearing journal surfaces, and to aluminum components. Uncontrolled electrical circuit paths can also cause electrical noise. Electrical noise may degrade the performance of the vessel and of the radio.The alternator, the starting motor, and all of the electrical systems MUST be grounded to the negative battery terminal. The alternator must meet marine isolation requirements. The starting motor must also meet marine isolation requirements.For engines which have an alternator that is grounded to an engine component, a ground strap MUST connect that component to the negative battery terminal and the component MUST be electrically isolated from the engine.A bus bar with a direct path to the negative "-" battery terminal is permissible and recommended for use for all components that require a negative "-" battery connection. The bus bar should be directly connected to the negative "-" battery terminal. A bonding cable should also be connected from the cylinder block to the bus bar on the negative "-" battery connection.Use of a bus bar ensures that the Electronic Control Module (ECM) and all of the components that are connected to the ECM have a common reference point.