The Cummins NT855 marine diesel engine is a legendary workhorse, celebrated for its durability, power, and reliability. Its robust design and proven performance make it a trusted choice for commercial vessels, fishing boats, and heavy-duty marine applications. With regular maintenance and care, the NT855 delivers exceptional service life, making it one of the most enduring engines in the Cummins marine lineup.

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Please note that these are typical maintenance intervals for the Marine Cummins NT855 engine, and some results may vary based on operating conditions. Adhering to these schedules is essential for ensuring reliable performance and extending the engine’s operational life.

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Marine Cummins NT855 Component Maintenance Life

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Component	Maintenance Interval (Hours)	Notes
Oil and Filter Change	250 hours	Regular oil changes are essential for maintaining engine lubrication and reducing wear.
Fuel Filters	500 hours	Replace regularly to ensure clean fuel delivery and prevent injector clogging.
Air Filters	500 hours	Inspect frequently and replace when dirty to protect engine performance.
Coolant	1,000 hours	Change to maintain optimal cooling and prevent corrosion in the system.
Injectors	2,000 hours	Inspect, clean, or replace to ensure efficient fuel combustion.
Valve Adjustment	1,500 hours	Regular adjustments are necessary to maintain proper engine timing and performance.
Turbocharger Inspection	2,000-3,000 hours	Inspect for wear; service or replace if necessary to maintain boost pressure.
Cylinder Head Overhaul	4,000-5,000 hours	Overhaul includes checking for wear, cracks, and ensuring proper sealing.
Piston Rings	6,000 hours	Replace during major service intervals to maintain compression and reduce oil consumption.
Crankshaft Bearings	6,000-8,000 hours	Inspect during overhauls; replace if signs of wear are evident.
Complete Engine Overhaul	10,000-12,000 hours	Comprehensive overhaul including pistons, liners, bearings, and other major components.

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Marine Cummins NT855 Coolant System Specific Component Maintenance Life

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Component	Maintenance Interval (Hours)	Notes
Coolant	1,000 hours	Change to maintain optimal cooling and prevent corrosion in the system.
Freshwater Pump	2,000-3,000 hours	Inspect for leaks, wear, and corrosion; replace seals or rebuild as necessary.
Raw Water Pump	500-1,000 hours	Inspect impeller for wear; replace impeller and seals as needed to maintain proper cooling.
Thermostats	1,500-2,000 hours	Inspect and test; replace if malfunctioning or during major coolant system service.

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Regular maintenance according to these intervals is crucial for the reliable performance of the Cummins NT855 engine in marine applications. Consistent inspections and timely servicing help extend the engine’s life and minimize the risk of unexpected breakdowns.

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Disclaimer: The most accurate data for each specific engine will always be found in the OEM service manual. The numbers provided here are estimates and can vary based on operating conditions. Factors such as inadequate cooling, lubrication, or fuel quality issues can affect other engine components, potentially altering maintenance intervals. Engine components are interconnected, so one issue can impact others, leading to different service needs. Always tailor your maintenance approach to the specific conditions in which your engine operates.

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Overview of the Cummins NT855

The NT855 is part of Cummins’ renowned N-Series engines. Designed for heavy-duty use, this six-cylinder engine boasts a displacement of 14 liters and offers outstanding torque and power output. The NT855 is a mechanical engine, ensuring straightforward operation and maintenance, particularly in environments where electronic systems may not be practical.

Key Features of the Cummins NT855

• Proven Mechanical Design
  The NT855’s mechanical fuel system and simple construction make it easy to operate and maintain, particularly in remote or demanding environments.
• High Torque Output
  Designed for heavy-duty applications, the NT855 delivers consistent power and torque, essential for towing, hauling, and long-haul operations.
• Durable Construction
  Engineered with marine-grade materials, the NT855 is built to withstand harsh marine environments, including saltwater exposure and extreme temperatures.
• Fuel Efficiency
  Despite its size and power, the NT855 is designed for efficient fuel consumption, making it cost-effective for extended operations.

Applications of the Cummins NT855 in Marine Settings

The versatility of the Cummins NT855 makes it an excellent choice for various marine applications, including:

• Commercial Fishing Boats
  The engine’s reliability and fuel efficiency ensure uninterrupted operation during extended fishing trips.
• Tugboats and Workboats
  With its high torque output, the NT855 is ideal for towing and other heavy-duty tasks in workboats.
• Passenger Ferries
  The NT855’s consistent performance and durability make it a reliable choice for passenger vessels operating in challenging conditions.
• Cargo Vessels
  The engine’s robust construction and efficiency make it suitable for cargo ships that require long-term, dependable power.

Maintenance Guidelines for the Cummins NT855

Proper maintenance is critical to keep the Cummins NT855 operating efficiently and to extend its service life. Adhering to a regular maintenance schedule minimizes the risk of unexpected failures and ensures optimal performance.

Key Maintenance Practices

1. Oil and Filter Changes
   • Replace the engine oil and oil filters every 250 hours of operation or as recommended.
   • Use high-quality oil to reduce wear on internal components and maintain lubrication.
2. Cooling System Maintenance
   • Flush and refill the cooling system regularly to prevent overheating and scale buildup.
   • Inspect the heat exchanger, raw water pump, and hoses for blockages or leaks, replacing worn components as necessary.
3. Fuel System Care
   • Replace fuel filters at regular intervals to ensure clean fuel delivery and prevent injector damage.
   • Use clean, high-quality diesel fuel to avoid contamination and maintain fuel system efficiency.
4. Turbocharger and Air Intake Maintenance
   • Inspect the turbocharger for excessive play or damage, ensuring proper airflow for optimal combustion.
   • Replace or clean air filters to maintain engine efficiency and prevent dust or debris from entering the system.
5. Valve Adjustments
   • Perform valve lash adjustments periodically to maintain proper valve timing and ensure efficient combustion.
6. Electrical System Checks
   • Inspect the starter, alternator, and wiring connections for wear or damage, ensuring reliable engine starts.
7. Belt and Hose Inspections
   • Regularly inspect belts and hoses for cracks, wear, or looseness, and replace them as needed to prevent failures.

Troubleshooting Common Issues

The Cummins NT855 is a durable and reliable engine, but occasional issues may arise. Below are some common problems and their potential solutions:

• Overheating
  • Cause: Blocked heat exchanger, worn impeller, or low coolant levels.
  • Solution: Clean the heat exchanger, replace the impeller, and refill the cooling system.
• Excessive Smoke
  • Cause: Black smoke indicates incomplete combustion, often due to dirty air filters, poor fuel quality, or injector issues.
  • Solution: Replace air filters, inspect injectors, and use high-quality fuel.
• Loss of Power
  • Cause: Turbocharger failure, clogged fuel lines, or dirty injectors.
  • Solution: Inspect the turbocharger, clean fuel lines, and replace worn injectors as necessary.
• Oil Leaks
  • Cause: Worn gaskets or seals, or excessive pressure in the crankcase.
  • Solution: Replace defective gaskets, check the crankcase ventilation system, and ensure proper torque on fasteners.

Benefits of Using Premium Aftermarket Parts for the NT855

Maintaining your Cummins NT855 with high-quality aftermarket parts ensures long-term reliability and performance. Diesel Pro Power offers a comprehensive range of aftermarket parts specifically designed for the NT855.

Why Choose Aftermarket Parts?

• Cost Savings
  Aftermarket parts are typically more affordable than OEM components, offering significant savings over the life of the engine.
• Availability
  Diesel Pro Power ensures a steady supply of aftermarket parts for the NT855, reducing downtime for marine operations.
• Enhanced Durability
  Many aftermarket parts are designed with updated materials and improved engineering to enhance durability and performance.
• Quality Assurance
  Diesel Pro Power’s aftermarket parts undergo rigorous testing to meet or exceed OEM standards, ensuring reliability in demanding conditions.

Technical Specifications of the Cummins NT855

Below are the key technical specifications of the Cummins NT855:

• Displacement: 14 liters (855 cubic inches)
• Bore and Stroke: 5.50 x 6.00 inches
• Power Output: 270–400 horsepower (depending on configuration)
• Compression Ratio: 14.5:1
• Dry Weight: Approximately 2,900 lbs

These specifications highlight the NT855’s capability to deliver consistent power and torque for a wide range of marine applications.