Common issues
- Cylinder liner and piston ring wear or scuffing from poor lube oil quality, fuel contamination or prolonged low-load running
- Exhaust valve and valve seat leakage or burning from deposits and thermal load, seen as rising exhaust temperature on the affected cylinder
- Fuel injection nozzle wear or fouling and fuel pump wear, causing smoke, afterburning and uneven cylinder load
- Turbocharger fouling or bearing wear reducing charge air pressure and raising exhaust gas temperatures
- Main bearing and big-end bearing wear from lube oil contamination or dilution, seen as falling oil pressure and metal debris in the filter
- Charge air cooler fouling raising charge air temperature and reducing engine output
- Cooling water system fouling, leaks or thermostat faults causing high jacket water temperature
Inspection checklist
- Review exhaust gas temperatures and the spread between all cylinders
- Check lube oil pressure, temperature and the condition of the filters, and review oil analysis trends
- Measure cylinder liner wear with a bore gauge at overhaul and compare with previous readings
- Inspect piston rings and ring grooves for wear, sticking and carbon build-up at each piston overhaul
- Check valve clearances and inspect exhaust valves and seats for burning or leakage
- Test fuel injectors for opening pressure and spray pattern, and check the fuel pumps for leakage
- Inspect turbocharger blading, bearings and the charge air cooler for fouling and pressure drop
- Check crankshaft deflection and main and big-end bearing condition at survey intervals
- Function-test the overspeed trip, low lube oil pressure and high coolant temperature shutdowns, and the crankcase oil mist detection
Service intervals
| Valve clearance check | typically every 1,000-2,000 running hours or per the maker's manual |
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| Fuel injector overhaul and testing | typically every 2,000-6,000 hours depending on fuel quality |
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| Piston and liner inspection | typically every 8,000-16,000 hours, or earlier on poor fuel or lube oil quality |
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| Turbocharger overhaul | per the maker's schedule, typically every 12,000-24,000 hours |
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| Lube oil and filter change | per oil analysis and the maker's schedule |
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| Crankshaft deflection check | at each major survey or dry-dock |
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Typical intervals for this design class, not the manufacturer’s figures for your model. The manufacturer’s manual is binding.
Typical wear limits
| Cylinder liner wear | reassess or renew when measured bore wear approaches the maker's stated limit - confirm against the manual rather than a generic figure |
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| Piston ring wear and ring groove clearance | compare against the maker's stated new and maximum clearances for this engine |
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| Bearing clearance | compare against the maker's stated new and maximum allowable clearance for this engine |
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Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Critical spares
- Piston rings and gudgeon pin bearings
- Exhaust valve and seat set
- Fuel injectors and nozzles
- Fuel pump plunger and barrel set
- Turbocharger bearing and seal kit
- Lube oil and fuel filter elements
- Cylinder head gaskets and O-rings
Safety
- Crankcase explosion risk from oil mist - keep crankcase relief devices and oil mist detection in working order
- High-pressure fuel lines and injectors can cause serious injury if opened under pressure
- Hot exhaust piping and turbocharger surfaces during and after operation
- Rotating shafts, flywheel and couplings - guards must be fitted and the engine locked out before work
- Heavy component lifting during overhaul of pistons, liners and cylinder heads
Class survey
Class typically reviews crankshaft deflection records, bearing and liner condition, turbocharger overhaul history, overspeed and shutdown tests and crankcase safety devices, and checks the engine's IMO NOx certificate.
Estimated lifetime: Medium-speed four-stroke engines of this class are generally designed for 20+ years of service and often well over 100,000 running hours in total, with periodic renewal of liners, rings, valves and bearings rather than whole-engine replacement