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Mitsubishi
6UEC68LSII
The Mitsubishi 6UEC68LSII is a six‑cylinder, low‑speed two‑stroke main propulsion engine delivering up to 24 300 kW at 93 rpm, featuring electronic control of fuel injection, exhaust valve and cylinder lubrication.
24300.0 kW
Power
Engine Specifications
6
Cylinders
680 mm
Bore
2200 mm
Stroke
24,300 kW
MCR Power
93.0 rpm
MCR RPM
2-stroke
Stroke Type
Family: Mitsubishi UEC (LS/LA/LSE/LSII)
· Tier: IMO Tier II
· Fuel: HFO, MDO
Inspector Detail
✓ verified
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Designation decoded
6-cylinder Mitsubishi UEC 68 cm bore, Long Stroke II (LSII) series. Crosshead two-stroke engine with conventional camshaft control and exhaust port scavenging, second generation of the long-stroke concept.
Background
The 6UEC68LSII shares the bore and stroke (680 × 2200 mm) with the 68LSE, but as an LSII variant is oriented toward the second generation of Mitsubishi's long-stroke development. The LSII series is characterized by improved components and extended service intervals. The 6-cylinder arrangement offers good vibration characteristics and is frequently used in Handymax and Panamax vessels.
Calculated metrics
Stroke To Bore Ratio
3.235
Inspector checklist
Zylinderinspektion
- Laufbuchsenverschleiß systematisch messen (4 Ebenen, 2 Achsen)
- Check piston rings for end gap and side clearance
- Examine piston crown for cracks, burnout and erosion
- Inspect exhaust ports for deposits and edge condition
Crosshead and running gear
- Kreuzkopflager-Spiel mit vorgeschriebener Methode messen
- Pleuelschrauben per Ultraschall-Längenmessung prüfen
- Inspect piston rod and stuffing box for wear and tightness
- Measure crankshaft deflection and compare with baseline values
Einspritzsystem
- Einspritzventile auf Prüfstand testen (Öffnungsdruck, Dichtheitstest, Strahlbildprüfung)
- Assess fuel pump wear (plunger/barrel)
- Nockenwellen-Steuerzeiten mit Technical File abgleichen
- Hochdruckleitungen auf Ermüdungsrisse prüfen
Abgassystem
- Examine exhaust valve spindle and seat for burn-off and corrosion
- Abgastemperaturen zwischen Zylindern vergleichen
- Turbolader-Wartungszustand (Schaufeln, Lager, Dichtungen) prüfen
- Inspect exhaust compensators and insulation
Control and safety
- Test overspeed protection and safety devices
- Check starting air valves for function and tightness
- Calibrate oil mist detector and verify alarm function
- Check reversing gear and remote control for proper operation
Logbook reference values
| Parameter | Expected | Deviation means |
|---|---|---|
| Exhaust gas temperature per cylinder | 340–420 °C | Elevated readings indicate injection or compression problems |
| Pmax-Zylindergleichmäßigkeit | ±3 bar vom Mittelwert | Deviations require injection and compression inspection |
| Spülluftdruck | 1.5–3.0 bar (lastabhängig) | Pressure drop indicates turbocharger or air cooler problems |
| Kühlwasser-Austrittstemperatur | 80–85 °C | Excessive readings indicate gas blow-by or scale formation |
| Zylinderöl-Feedrate | 0.7–1.2 g/kWh | Deviations affect wear and deposit formation |
| Systemöl-Druck | 2.5–4.5 bar | Pressure drop may indicate filter blockage or bearing damage |
Common Failure Modes
Laufbuchsen-Micro-Seizure
Symptoms: ['Vertikale Riefenbildung auf der Laufbuchse', 'Increased wear', 'Kolbenring-Bruch']
Causes: Unzureichende Zylinderöl-Versorgung, Zu schnelle Lastaufnahme, Wassereinbruch in den Zylinder
Preventive: Zylinderöl-Dosierung überwachen, Lastaufnahmeprogramm gemäß Herstellervorgabe einhalten, Spülluftkasten regelmäßig inspizieren
Abgasventil-Undichtigkeit
Symptoms: ['Erhöhte Abgastemperatur', 'Leistungsverlust des betroffenen Zylinders', 'Hörbare Leckage']
Causes: Hot corrosion due to vanadium in heavy fuel oil, Mangelhafte Ventildrehung, Seat damage from foreign objects
Preventive: Check valve rotation device at each inspection, regularly lap seating surfaces, optimize fuel treatment
Grundlager-Schaden
Symptoms: ['Erhöhte Lagertemperatur', 'Metallpartikel im Schmieröl', 'Veränderte Deflection-Werte']
Causes: Schmierölverunreinigung, Misalignment due to hull deformation, Materialermüdung
Preventive: Perform lubricating oil analyses, measure and document deflection values regularly, inspect main bearing at major overhaul
Nockenwellen-Kettenlängung
Symptoms: ['Veränderte Steuerzeiten', 'Geräusche im Kettenkasten', 'Unruhiger Motorlauf']
Causes: High operating hours, Unzureichende Kettenschmierung, Sprocket wear
Preventive: Measure chain elongation at prescribed intervals, replace if >1 %, monitor chain tensioner function
Expert tips
- 💡 Improved materials were used in LSII engines – always use the LSII-specific part number when ordering spare parts, not that of the predecessor model.
- 💡 The 6-cylinder LSII configuration has factory-optimized counterweights – check the balance protocol after crankshaft work.
- 💡 Extended service intervals of the LSII series by the manufacturer should only be maintained upon proof of prescribed operating conditions (oil quality, fuel, load).
Related components
Turbocharger (MHI or compatible)
Charge air cooler and water separator
Brennstoffaufbereitung (Separatoren, Heizer, Filter)
Camshaft drive and chain tensioner
Zylinderöl-Dosiereinheiten
Kolbenkühlöl-Teleskoprohre
Main bearing and thrust bearing
Reversing coupling and control air
Classification & regulatory
IMO NOx Tier II according to MARPOL Annex VI to be demonstrated. Technical File must document current engine settings. Camshaft-controlled fuel injection is specified in the Technical File – modifications require class approval and, if necessary, NOx re-measurement. From 2018 J-ENG as manufacturer – ensure service documentation and spare parts availability through updated channels.
Reference content for inspector orientation. Always verify against manufacturer's manual, latest service letters and class society requirements.
Other Cylinder Configurations 44
5UEC33LSE
5 cyl
· 3,100 kW
5UEC37LA
5 cyl
· 4,250 kW
5UEC43LSE
5 cyl
· 6,000 kW
5UEC45LA
5 cyl
· 7,000 kW
5UEC50LSE
5 cyl
· 9,250 kW
5UEC50LSII
5 cyl
· 9,500 kW
5UEC52LA
5 cyl
· 10,250 kW
5UEC60LS
5 cyl
· 14,500 kW
5UEC60LSII
5 cyl
· 15,250 kW
5UEC68LSE
5 cyl
· 19,500 kW
5UEC68LSII
5 cyl
· 20,250 kW
5UEC85LSII
5 cyl
· 29,000 kW
6UEC33LSE
6 cyl
· 2,100 kW
6UEC37LA
6 cyl
· 5,100 kW
6UEC43LSE
6 cyl
· 7,200 kW
6UEC45LA
6 cyl
· 5,610 kW
6UEC50LSE
6 cyl
· 7,320 kW
6UEC50LSII
6 cyl
· 11,400 kW
6UEC52LA
6 cyl
· 12,300 kW
6UEC60LS
6 cyl
· 17,400 kW
6UEC60LSII
6 cyl
· 18,300 kW
6UEC68LSE
6 cyl
· 23,400 kW
6UEC85LSII
6 cyl
· 22,680 kW
7UEC33LSE
7 cyl
· 4,340 kW
7UEC37LA
7 cyl
· 5,950 kW
7UEC43LSE
7 cyl
· 8,400 kW
7UEC45LA
7 cyl
· 9,800 kW
7UEC50LSE
7 cyl
· 12,950 kW
7UEC50LSII
7 cyl
· 13,300 kW
7UEC52LA
7 cyl
· 14,350 kW
7UEC60LS
7 cyl
· 14,420 kW
7UEC60LSII
7 cyl
· 21,350 kW
7UEC68LSE
7 cyl
· 27,300 kW
7UEC68LSII
7 cyl
· 28,350 kW
7UEC85LSII
7 cyl
· 40,600 kW
8UEC33LSE
8 cyl
· 4,960 kW
8UEC43LSE
8 cyl
· 9,600 kW
8UEC45LA
8 cyl
· 11,200 kW
8UEC50LSE
8 cyl
· 14,800 kW
8UEC50LSII
8 cyl
· 15,200 kW
8UEC52LA
8 cyl
· 16,400 kW
8UEC60LSII
8 cyl
· 24,400 kW
8UEC68LSII
8 cyl
· 32,400 kW
8UEC85LSII
8 cyl
· 46,400 kW
Components & Design
Component data being added…
Technical Data
SFOC (UEC60LSE-Eco-A2)
164-170 g/kWh (IMO Tier II)
BMEP (UEC60LSE)
20.0-21.0 bar @ MCR
Piston speed (UEC60LSE)
8.4 m/s
Dry mass UEC60LSE 8-cyl
447 tons
Dry mass UEC60LSE 5-cyl
300 tons
Bore/Stroke ratio UEC60LSE
4.00
Stroke/Bore UEC68LSE
3.96
Electronically controlled
Fuel injection, exhaust valve, cylinder lubrication (ECL)
unified from engine model
True
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Common failures & inspection points
Exhaust valve fouling due to sodium/vanadium deposits (Na2SO4, CaSO4, V2O5) with heavy fuel oil containing high sulphur content (up to 5%); below dew point conden
Turbocharger fouling due to coal and ash particles in exhaust gas during low-load operation, BMEP decline and combustion deterioration
Piston ring leakage and fuel dilution (>2-3%) due to wear on cylinder running surface/piston rings, increased blowby and oil contamination
Cylinder liner wear due to corrosive combustion with sulphurous fuel oil; inspection criterion: wear according to height of sliding surface, max. permissible
Main bearing wear due to oil contamination; weekly inspection for water ingress (<2% permissible) and 3-month analysis for wear metals (Fe, Cu) required
Type-general inspection and maintenance points for this equipment category — not model-specific.
Suppliers & Spare Parts
Direct links to manufacturer, datasheet, spare-parts portal and dealers — request access below.
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Equipment Model #38594
· ✓ still in production