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Mitsubishi

7UEC68LSE

Name: Mitsubishi 7UEC68LSE
Brand: Mitsubishi
SKU: OSE-38605

The Mitsubishi UEC68LSE is a 7‑cylinder, low‑speed two‑stroke main engine delivering up to 27,300 kW at 93 rpm, featuring electronic control of fuel injection and exhaust valves for IMO Tier II compliance.

27300.0 kW

Power

Engine Specifications

Cylinders

680 mm

Bore

2200 mm

Stroke

27,300 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

▸

Designation decoded

7UEC68LSE – Mitsubishi 7-Zylinder, Unified Exhaust-valve Crosshead, 680 mm Bohrung, LSE-Baureihe. Zweitakt-Kreuzkopfmotor mit Nockenwellensteuerung. 7-Zylinder-Konfiguration erfordert besondere Aufmerksamkeit hinsichtlich Torsionsschwingungen der Kurbelwelle.

Background

The UEC68LSE belongs to the LSE generation of Mitsubishi UEC large engines. The 680 mm bore class represents a medium-sized slow-speed engine, commonly used in bulk carriers and medium-sized tankers. The LSE variant offers improved fuel efficiency and optimized exhaust emissions compared to the base LS series. As a 7-cylinder configuration, this engine requires particular attention to the torsional vibration damper and vibration monitoring, since odd cylinder numbers in this engine series tend to exhibit increased torsional vibrations. The camshaft control requires regular checking of valve timing and camshaft condition.

Calculated metrics

Stroke To Bore Ratio

3.235

Mean Effective Pressure Bar

19.5

Inspector checklist

Crankshaft and torsion vibration damper

Torsionsschwingungsdämpfer auf Silikonöl-Leckage prüfen
Measure crankshaft deflection and compare with limit values
Axialspiel der Kurbelwelle am Drucklager messen
Assess main bearing condition by inspection and oil analysis

Cylinder liners and pistons

Determine liner wear by micrometer measurement at multiple levels
Check piston rings for wear, end gap and free movement
Inspect piston crown for cracks and scorch marks
Check cylinder oil supply and lubrication rate

Camshaft and valve control

Inspect camshaft lobes for pitting and wear
Check exhaust valve timing and document
Inspect rocker arms and roller bearings for wear
Check camshaft drive chain or gears for wear and backlash

Crosshead and connecting rod

Kreuzkopflagerspiel messen
Inspect crosshead guide shoe for wear and cracking
Schubstangenlager inspizieren
Teleskoprohre der Kolbenkühlung auf Dichtheit prüfen

Exhaust valves and turbocharger

Inspect exhaust valve spindle and seat for corrosion and erosion
Ventildrehvorrichtung auf Funktion testen
Document turbocharger speed and boost pressure
Ladeluftkühlerwirkungsgrad bestimmen

Logbook reference values

Parameter	Expected	Deviation means
Maximaler Zünddruck (Pmax)	140–155 bar	Deviation indicates faulty injection, worn piston rings or incorrect valve timing
Kompressionsdruck (Pcomp)	115–130 bar	Low value indicates leaking exhaust valves, worn piston rings or liner wear
Exhaust gas temperature per cylinder	330–400 °C	Elevated temperature indicates poor combustion, defective injectors or uneven load distribution
Zylinderölverbrauch	0,9–1,3 g/kWh	Zu hoher Verbrauch deutet auf Laufbuchsenverschleiß hin; zu niedriger Verbrauch erhöht Korrosionsgefahr
Kühlwasseraustrittstemperatur Zylinder	80–85 °C	Excessive temperature may indicate deposits in the cooling jacket or cracks in the liner
Kurbelwellendurchbiegung	±0,05 mm (Betriebszustand)	Exceeding indicates main bearing wear, foundation settlement or hull deformation
Spülluftdruck	2,0–2,8 bar (Volllast)	Low pressure indicates turbocharger fouling or charge air cooler blockage

Common Failure Modes

Rissbildung an der Kolbenkrone

Symptoms: ['Erhöhte Abgastemperatur am betroffenen Zylinder', 'Kühlöltemperaturanstieg', 'Ölnebel im Kurbelgehäuse']

Causes: Thermal fatigue due to repeated load changes, Unzureichende Kolbenkühlung, Defekte Einspritzdüsen mit Nachverbrennung

Preventive: Regular endoscopy of piston crown at each piston removal, minimize thermal stress through even load build-up

Auslassventilsitzkorrosion

Symptoms: ['Increasing pressure loss during compression', 'Erhöhte Abgastemperatur', 'Verschlechterte Brennstoffeffizienz']

Causes: High-temperature corrosion due to vanadium and sodium in fuel, Ungenügende Ventildrehung, Falsche Verbrennungstemperaturen

Preventive: Monitor fuel quality, check valve rotation device regularly, rework valve seats during overhaul per manufacturer specification

Camshaft wear and pitting

Symptoms: ['Unregelmäßige Einspritzcharakteristik', 'Veränderte Steuerzeiten', 'Schwankende Zylinderdrücke']

Causes: Unzureichende Schmierung der Nockenwelle, Ermüdung der Nockenoberfläche, Kontaminiertes Schmieröl

Preventive: Ensure lubricating oil quality and quantity per manufacturer specifications, perform regular visual inspection of cam surfaces

Torsionsschwingungsdämpfer-Versagen

Symptoms: ['Erhöhte Schwingungswerte an der Kurbelwelle', 'Ungewöhnliche Geräusche am freien Wellenende', 'Silikonölaustritt am Dämpfergehäuse']

Causes: Alterung des Silikonfluids, Überschreitung der Betriebsstundenlimit ohne Revision, Materialer müdung der Dämpferbauteile

Preventive: Check silicone viscosity per manufacturer intervals, revise damper after maximum 50,000 operating hours, perform vibration measurements regularly

Expert tips

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Related components

Torsionsschwingungsdämpfer Fuel injection pumps and nozzles Turbocharger and charge air cooler Zylinderöl-Dosiereinheit Crosshead bearings and guides Auslassventil-Hydrauliksystem Control air and starting air valves Main frame and engine foundation

Classification & regulatory

Torsional vibration analysis must be documented per classification society requirements. The vibration damper is subject to special survey. During cylinder inspections, wear limits of the classification society for running gear liners and piston rings must be observed. From the LSE generation onwards, stricter NOx emission limit values apply (IMO Tier II). The EIAPP certification (Engine International Air Pollution Prevention) and the associated Technical File must be available on board and updated when changes occur.

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

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

marineengineeringonline.com/main-en...

Turbocharger fouling due to coal and ash particles in exhaust gas during low-load operation, BMEP decline and combustion deterioration

marineengineeringonline.com/fouling...

Piston ring leakage and fuel dilution (>2-3%) due to wear on cylinder running surface/piston rings, increased blowby and oil contamination

www.marineinsight.com/main-engine/e...

Cylinder liner wear due to corrosive combustion with sulphurous fuel oil; inspection criterion: wear according to height of sliding surface, max. permissible

www.goseamarine.com/marine-engine-s...

Main bearing wear due to oil contamination; weekly inspection for water ingress (<2% permissible) and 3-month analysis for wear metals (Fe, Cu) required

www.marineinsight.com/main-engine/e...

Type-general inspection and maintenance points for this equipment category — not model-specific.

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Equipment Model #38605 · ✓ still in production