Main Engine 4-Stroke · Main Engines (4-Stroke)
The Wärtsilä 20 is a medium‑speed four‑stroke marine diesel/dual‑fuel main engine series (200 mm bore × 280 mm stroke) offered in 4L‑9L per cylinder variants, operating at 900–1200 rpm and delivering up to ~220 kW per cylinder.
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What our service work and the manufacturer documentation say about keeping this model running.
Commonly maintained by scheduled minor and major overhauls according to Wärtsilä running-hour plan.
| Fuel Injector Overhaul | 3,000 - 6,000 running hours |
|---|---|
| Cylinder Head Overhaul (valves, springs, seats) | 8,000 - 12,000 running hours |
| Fuel Pump Overhaul | 8,000 - 12,000 running hours |
| Piston Withdrawal & Inspection | 16,000 - 24,000 running hours |
| Main & Crankpin Bearing Inspection | 24,000 - 36,000 running hours |
| Turbocharger Overhaul | 12,000 - 24,000 running hours |
| Cylinder Liner Wear | Max 0.6 - 0.8 mm ovality or diameter increase from new. |
|---|---|
| Piston Ring Axial Clearance | Max 0.15 - 0.2 mm increase from new in groove. |
| Crankshaft Deflection | Max 0.05 mm (difference between readings at various crank positions). |
| Main/Crankpin Bearing Clearance | Max 0.15 - 0.25 mm (depending on bearing size). |
| Exhaust Valve Seat Recession | Max 0.5 - 1.0 mm from cylinder head surface. |
| Fuel Injector Opening Pressure | +/- 5-10 bar from specified nominal pressure. |
Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Class surveyors typically verify the engine's compliance with statutory and classification rules. Key checks include: verification of planned maintenance system (PMS) records and running hours; crankshaft deflection measurements (as per class schedule); inspection and testing of safety devices (overspeed, low lube oil pressure, high cooling water temperature shutdowns, emergency stops); general condition of the engine, absence of leaks, and cleanliness; integrity of fuel oil and lube oil systems (piping, bunkering arrangements, fire prevention measures); exhaust gas system integrity (insulation, expansion joints); main bearing and crankpin bearing inspection (at specified intervals, often coinciding with major overhaul); cylinder liner wear measurements; and functionality of local and remote controls.
Estimated lifetime: 24,000 - 36,000 running hours before major overhaul (piston withdrawal, bearing inspection)
Injector sets, exhaust valves, head gasket kits, filters, thermostats and turbocharger overhaul kits are common stock items.
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