Main Engine 4-Stroke · Main Engines (4-Stroke)
The 20V4000 M73 is a high-power marine diesel engine designed for demanding applications. Manufactured by MTU, this engine offers a power output of 3300 kilowatts and is configured in a V-type layout with 20 cylinders. Capable of operating on marine diesel ISO 8217, it features a 4-stroke cycle and sequential turbocharging with two water-cooled turboladers. The MTU 20V4000 M73 has been in production since 1996, with over 58,000 units sold worldwide and more than 345 million operating hours accumulated. Common failures include issues with water intake pump seals leading to corrosion, turbocharger failures due to lubrication problems, contamination of fuel by water or biological growth, internal corrosion in water-cooled exhaust manifolds, and neglect of cooling systems resulting in overheating events.
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| Lube oil and filter change | per maker's schedule, typically every 500-1,000 hours depending on oil analysis |
|---|---|
| Fuel filter change | every 500 hours or per differential pressure indication |
| Valve clearance check | typically every 1,000-2,000 hours |
| Injector inspection or testing | typically every 4,000-6,000 hours, duty dependent |
| Turbocharger inspection | typically every 8,000-12,000 hours or per maker's schedule |
| Major overhaul, top end | engine-hours dependent per the MTU maintenance schedule |
Typical intervals for this design class, not the manufacturer’s figures for your model. The manufacturer’s manual is binding.
| Cylinder liner wear | wear limits are bore-class and maker specific, typically a few tenths of a millimetre over standard bore for engines this size - confirm against the MTU maintenance manual rather than a generic figure |
|---|---|
| Piston ring end gap | typically in the order of 0.3-0.6 mm per ring for this bore class when new; the condemning limit is per the maker's manual, confirm before condemning a ring |
Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Under Continuous Survey Machinery, class typically reviews running hour logs, crankshaft deflection readings where applicable, oil analysis trends and completed condition-based maintenance items rather than opening the engine on a fixed calendar basis.
Estimated lifetime: Medium-speed engines of this class are typically designed toward a major overhaul interval in the order of 20,000-30,000 running hours between top overhauls, strongly dependent on load and fuel quality - confirm against MTU's maintenance schedule for the 4000 series
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