6UEC50LSII
The Mitsubishi 6UEC50LSII is a six‑cylinder, low‑speed 2‑stroke main engine delivering up to 11.4 MW at around 124 rpm, noted for its high specific power and fuel‑efficiency (≈167 g/kWh) in bulk carrier and tanker applications.
Engine Specifications
Inspector Detail
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Designation decoded
6 = Anzahl der Zylinder (6-Zylinder-Reihenmotor), UEC = Unified Exhaust-port Crosshead (Zweitakt-Kreuzkopfmotor-Baureihe von Mitsubishi), 50 = Zylinderbohrung in cm (500 mm), LSII = Long Stroke II (zweite Generation der langhubigen Ausführung)
Background
The 6UEC50LSII is a 6-cylinder two-stroke crosshead engine of the second long-stroke generation with 500 mm bore and 1600 mm stroke. Compared to the previous generation, the LSII version offers improved mechanical efficiency with conventional camshaft control. The engine is manufactured by Mitsubishi Heavy Industries / J-ENG and is designed as main propulsion for bulk carriers and general cargo ships.
Calculated metrics
Inspector checklist
- Perform bore gauging and determine wear rates per 1000 operating hours
- Check piston rings for coating condition, end gap and side clearance
- Inspect piston crown for hot cracks and combustion bowl erosion
- Measure and document crosshead bearing clearance
- Kreuzkopfbolzen per NDT auf Oberflächenrisse prüfen
- Check connecting rod bolt elongation and marking alignment
- Kurbelwellen-Deflection aufnehmen
- Camshaft chain drive: monitor chain elongation and sprocket profile
- Inspect fuel and exhaust cams for pitting and wear
- Steuerzeiten gegen Herstellerangaben abgleichen
- Check valve seat and spindle for erosion and vanadium corrosion
- Rotocap-Funktion testen
- Ventilführungsspiel messen
- Fuel injectors: verify opening pressure and spray pattern
- Check fuel pump plunger for wear
- Hochdruckleitungen auf Schwingungsrisse inspizieren
Logbook reference values
| Parameter | Expected | Deviation means |
|---|---|---|
| Abgastemperatur je Zylinder | 310–375 °C at rated load | Deviations indicate fuel injection, compression, or valve problems |
| Max. Zünddruck (Pmax) | Gemäß Herstellerangabe ± 5 bar | Lower Pmax indicates compression loss or timing error |
| Spülluftdruck | 1,8–3,0 bar (lastabhängig) | Zu niedriger Wert weist auf Turbolader-Degradation hin |
| Zylinderöl-Verbrauch | 0,5–1,0 g/kWh | Increased consumption signals progressive wear |
| Kühlwasseraustrittstemperatur | 78–85 °C | Abweichung deutet auf Kühlsystemprobleme hin |
| Schmieröldruck Hauptlager | 3,0–4,5 bar | Pressure drop indicates bearing wear or pump problems |
Common Failure Modes
Expert tips
- 💡 The LSII version has improved liner geometry compared to the LS first version – when replacing, always use the correct part number of the LSII specification.
- 💡 At S/B ratio of 3.2 and 6-cylinder configuration, regularly monitor axial vibrations in the engine – check torsion damper silicone condition.
- 💡 At part load operation, configure turbocharger cut-out correctly on multi-turbo installations to avoid surging.
Related components
Classification & regulatory
Inspection and maintenance in accordance with the requirements of the applicable classification society. Consult NOx Technical File and EIAPP certificate when overhauling NOx-relevant components. For ships with EEDI requirements: align performance parameters after overhaul with EEDI reference values.
Reference content for inspector orientation. Always verify against manufacturer's manual, latest service letters and class society requirements.
Other Cylinder Configurations 44
Components & Design
Component data being added…
Technical Data
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Common failures & inspection points
Borescope inspection of exhaust valve seats for scratches/wear, dye penetrant test for cracks, leakage measurements (valve should hold pressure under compressed air for 15 min)
Liner surface inspection for scratches/grooves, piston run gemietlich measurement, lubricant flow rate check (wrong parameters for part load operation)
Measure pressure drop across cooler, check air temperature after cooler, inspect drainage separator for water accumulation
Tägliche Kurbelgehäuse-Ölprobe auf Weißmetall-Partikel (>0.5 mm mit glatter Oberfläche beidseitig = Überbelastung), Lagerspiel-Kontrolle per Schieblehre
Check crankshaft bearing flanges with magnifying glass for cracks; crankshaft deflection measurement via dial gauge (indicator set: <0.1 mm critical)
Type-general inspection and maintenance points for this equipment category — not model-specific.
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