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MAN Energy Solutions
7S90MC-C8
The MAN 7S90MC-C8 is a low‑speed, two‑stroke marine diesel main engine delivering up to 90 MW at 76 rpm, featuring camshaft‑controlled fuel injection and constant‑pressure turbocharging for high efficiency and reliability.
90090.0 kW
Power
Engine Specifications
7
Cylinders
900 mm
Bore
3260 mm
Stroke
90,090 kW
MCR Power
76.0 rpm
MCR RPM
2-stroke
Stroke Type
Family: MAN B&W MC/MC-C
· Tier: Tier II
· Fuel: HFO, VLSFO, MDO
Inspector Detail
✓ verified
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Designation decoded
7 stands for 7 cylinders, S for Super-Long-Stroke, 90 for 900 mm bore, MC-C for the MAN B&W MC Compact series, 8 for Mark 8.
Background
The S90MC-C8 is the Super-Long-Stroke variant of the 90-class bore with an impressive 3,260 mm stroke. One of the largest marine engines in the MC/MC-C series, used in VLCCs, ULCCs and the largest Capesize bulkers. S/B 3.62 for the lowest speeds and maximum propulsive efficiency.
Calculated metrics
Stroke To Bore Ratio
3.622
Inspector checklist
Running gear & tribology
- Cylinder liners: enormous dimensions at 900 mm bore and 3,260 mm stroke — wear measurement with precision instruments required at a minimum of 8 positions
- Piston rings: significant lateral forces at S/B 3.62 — pay particular attention to thrust-side wear
- Piston cooling: shaker cooling efficiency critical with a long stroke — check oil temperatures at the piston crown
Crosshead & stuffing box
- Crosshead bearing: extreme inertial forces at 3,260 mm stroke — bearing temperature is the most critical parameter
- Stuffing box: long stroke = high relative motion = increased wear — shorter inspection intervals than K/L variants
- Piston rod condition and deflection
Control & hydraulics
- Camshaft drive: extreme load from long strokes and large masses
- Exhaust valve: large dimensions — check actuating cylinder and hydraulics for leakage
- Injection pumps: timing precision decisive on a large engine for emissions and economy
Scavenge air & exhaust system
- Scavenge air box: walk-in — systematic inspection of all 7 cylinder ports
- Turbocharger: 2- or 3-TC configuration possible — check all units
- Exhaust economiser: increased soot fire risk at part load
Sealing systems
- Cylinder cover: large sealing faces, high bolt forces — torque control
- Exhaust valve seat: accelerated wear at high thermal load
- Cooling water connections for leakage
Logbook reference values
| Parameter | Expected | Deviation means |
|---|---|---|
| Exhaust gas temperature after cylinder | 350-420 °C at MCR | Spread >20 °C → systematic root cause analysis |
| Scavenge air pressure | 2.5-3.2 bar | Drop → check turbocharger |
| Pmax | ±3 bar cylinder balance | Deviation → timing/compression |
| Crosshead bearing temperature | 55-65 °C | Rise >5 °C → investigate immediately |
| Cooling water temperature | 80-85 °C | Check single-cylinder deviation |
| Cylinder oil feed rate | 0.6-1.0 g/kWh | Adjust to fuel |
Common Failure Modes
Crosshead bearing overload
Symptoms: Temperature rise, metal particles in the oil filter, increasing bearing clearance
Causes: Extreme inertial forces at 3,260 mm stroke, Insufficient oil supply, Crankshaft deflection outside tolerance
Preventive: Measure deflection quarterly, verify oil supply at every inspection
Scavenge air box fire
Symptoms: Temperature rise, smoke, alarm
Causes: Oil accumulation from stuffing box leakage at the long stroke, Piston ring blow-by, Part-load operation
Preventive: Inspect and clean scavenge air box every 1,000-2,000 Bh, keep drainage functional
Cold wear at the 900 mm liner
Symptoms: Increased wear rate, rough surface
Causes: Cooling water below dew point, Feed rate/BN mismatch
Preventive: Cooling water >65 °C, match feed rate and BN to fuel
Expert tips
- 💡 With the S90MC-C8's 3,260 mm stroke, scavenge air box inspection is especially important — the long stroke leads to more stuffing box wear and thus more oil entering the scavenge air box. Shorten the inspection interval to 1,000 Bh during slow steaming
- 💡 The 900 mm liner weighs over 6 tons — replacement requires yard time and special tools. Carefully track the wear trend to make replacement plannable
- 💡 With a 2-TC configuration and slow steaming: regularly test the TC cut-out procedure to be able to react quickly if needed
Related components
Turbocharger (2- or 3-TC configuration)
Scavenge air cooler (large dimensions)
Exhaust economiser
Shaft line, propeller and thrust bearing
Foundation bolts and double bottom structure
Classification & regulatory
IMO Tier I compliant. Combustion optimization and possibly EGR/SCR required for Tier II. EEDI requirements particularly relevant on large ships. MARPOL Annex VI — scrubber retrofits common on VLCCs.
Reference content for inspector orientation. Always verify against manufacturer's manual, latest service letters and class society requirements.
Other Cylinder Configurations 50
5L35MC-C8
5 cyl
· 6,450 kW
5L42MC-C8
5 cyl
· 10,100 kW
5L60MC-C8
5 cyl
· 21,000 kW
5L70MC-C8
5 cyl
· 31,150 kW
5L80MC-C8
5 cyl
· 42,000 kW
5S26MC-C8
5 cyl
· 3,700 kW
5S35MC-C8
5 cyl
· 7,650 kW
5S42MC-C8
5 cyl
· 12,950 kW
5S46MC-C8
5 cyl
· 15,500 kW
5S50MC-C8
5 cyl
· 18,650 kW
5S60MC-C8
5 cyl
· 28,250 kW
5S65MC-C8
5 cyl
· 35,000 kW
5S70MC-C8
5 cyl
· 40,400 kW
5S80MC-C8
5 cyl
· 51,000 kW
5S90MC-C8
5 cyl
· 64,350 kW
6K80MC-C8
6 cyl
· 43,500 kW
6K90MC-C6
6 cyl
· 30,780 kW
6K90MC-C8
6 cyl
· 56,700 kW
6K98MC-C8
6 cyl
· 85,020 kW
6L35MC-C8
6 cyl
· 7,740 kW
6L42MC-C8
6 cyl
· 12,120 kW
6L60MC-C8
6 cyl
· 25,200 kW
6L70MC-C8
6 cyl
· 37,380 kW
6L80MC-C8
6 cyl
· 50,400 kW
6S26MC-C8
6 cyl
· 4,440 kW
6S35MC-C8
6 cyl
· 9,180 kW
6S42MC-C8
6 cyl
· 15,540 kW
6S46MC-C8
6 cyl
· 18,600 kW
6S50MC-C8
6 cyl
· 22,380 kW
6S50MC-C8.2
6 cyl
· 9,960 kW
6S60MC-C8
6 cyl
· 33,900 kW
6S65MC-C8
6 cyl
· 42,000 kW
6S65MC-C8.2
6 cyl
· 16,440 kW
6S70MC-C8
6 cyl
· 48,480 kW
6S80MC-C8
6 cyl
· 61,200 kW
6S90MC-C8
6 cyl
· 77,220 kW
7K80MC-C6
7 cyl
· 28,980 kW
7K80MC-C8
7 cyl
· 50,750 kW
7K90MC-C8
7 cyl
· 66,150 kW
7K98MC-C7.1
7 cyl
· 40,040 kW
7K98MC-C8
7 cyl
· 99,190 kW
7L35MC-C8
7 cyl
· 9,030 kW
7L42MC-C8
7 cyl
· 14,140 kW
7L60MC-C8
7 cyl
· 29,400 kW
7L70MC-C8
7 cyl
· 43,610 kW
7L80MC-C8
7 cyl
· 58,800 kW
7S35MC-C8
7 cyl
· 10,710 kW
7S42MC-C8
7 cyl
· 18,130 kW
7S46MC-C8
7 cyl
· 21,700 kW
7S50MC-C8
7 cyl
· 26,110 kW
Components & Design
Component data being added…
Technical Data
unified from engine model
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Maritime Network →Manuals
-
operating
MAN B&W MC/MC-C Engine Operating Manual (OM-MC-C)MAN Energy Solutions
-
maintenance
MAN B&W MC/MC-C Maintenance Manual (MM-MC-C)MAN Energy Solutions
-
spare_parts
MAN B&W MC/MC-C Illustrated Parts Catalogue (IPC-MC-C)MAN Energy Solutions
-
project_guide
MAN B&W Project Guide MC/MC-C (PG-MC-C)MAN Energy Solutions
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Equipment Model #38242
· ✓ still in production