Auxiliary engines are essential for powering onboard systems, generators, pumps, navigation equipment, and critical vessel operations. When major components such as the engine block and crankshaft suffer excessive wear or damage, a complete overhaul becomes necessary to restore reliability, performance, and operational safety.
At Marine and Industrial Solutions LLC (MI Solutions), our engineering team recently completed a major overhaul of a Cummins NT855 Auxiliary Marine Engine. The scope included renewal of the engine block and crankshaft, overhaul and pressure testing of cylinder heads, installation of genuine Cummins spare parts, turbocharger replacement, fuel system refurbishment, onboard installation, alignment, commissioning, and load testing.
This article explains the overhaul process, highlights the warning signs that indicate a major engine rebuild is required, and demonstrates how our marine mechanical engineering team in Dubai restored the Cummins NT855 engine to reliable operating condition.
What Is a Cummins NT855 Auxiliary Marine Engine?
The Cummins NT855 is a heavy-duty diesel engine widely used in marine auxiliary applications due to its durability, fuel efficiency, and dependable performance. These engines operate continuously in demanding environments and are exposed to high temperatures, heavy loads, vibration, and corrosive marine conditions.
Over time, critical components such as crankshafts, bearings, cylinder liners, pistons, and cylinder heads experience wear that can eventually impact engine performance and reliability. A professionally executed overhaul restores the engine to OEM operating standards and significantly extends service life.
Inspection Findings Before Overhaul
Following dismantling and inspection of the Cummins NT855 engine, several critical defects were identified:
- Engine block found with severe physical damage beyond repair limits.
- Crankshaft journals and bearing surfaces showed significant wear and scoring.
- Camshaft roller contact areas exhibited excessive wear.
- Cylinder heads required complete overhaul and pressure testing.
- Pistons, connecting rods, liners, bearings, valves, turbocharger, and fuel system components required renewal.
Based on these findings, a complete engine rebuild with engine block and crankshaft replacement was recommended to restore safe and reliable operation.
Our Cummins NT855 Major Overhaul Process
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Step 1
Complete Dismantling & AssessmentThe engine was fully dismantled and all major components were cleaned, measured, inspected, and documented. Critical dimensions were verified to determine serviceability and identify components requiring replacement. |
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Step 2
Engine Block & Crankshaft RenewalThe damaged engine block and worn crankshaft were replaced with genuine Cummins components. New main bearings, thrust bearings, and bearing shells were installed according to OEM specifications to ensure correct alignment and lubrication. |
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Step 3
Cylinder Head Overhaul & Pressure TestingAll cylinder heads were overhauled with new intake valves, exhaust valves, valve guides, springs, and sealing components. Each head was pressure tested before assembly to ensure leak-free operation. |
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Step 4
Installation of Genuine Cummins Spare PartsNew pistons, connecting rods, piston rings, cylinder liners, turbocharger, fuel pump, filters, gaskets, and O-rings were installed. All replacement components were genuine Cummins parts supplied through MIS. |
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Step 5
Onboard Installation & CommissioningThe rebuilt engine was transferred onboard, aligned with the alternator, connected to cooling and lubrication systems, and commissioned according to OEM procedures. |
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Step 6
Engine Run Test & Performance VerificationThe engine successfully completed no-load and load testing. Lubrication pressure, temperatures, cooling system performance, and overall engine operation remained within acceptable operating limits, confirming successful overhaul completion. |
Related Services: Machine Shop Services | Marine Mechanical Services | Marine Spare Parts Supply | Marine Electrical Services