Cummins QSK19 marine engine spare parts

AMS Parts · Cummins marine engine guide

The Cummins QSK19 is the electronically controlled evolution of the K19 platform — a 19-litre in-line six delivering 500–800 hp in marine configuration. Built for commercial marine duty where the mechanical K-series previously dominated, it brings Cummins' Modular Common Rail fuel system and modern engine management to a proven heavy-duty architecture.

It remains one of the most widely operated high-horsepower marine engines in commercial fleets worldwide. This guide covers its applications, the parts it most commonly requires, and the technical detail needed to specify components correctly.

What is the Cummins QSK19 marine engine?

The QSK19 is an in-line six-cylinder, four-stroke diesel displacing 19 litres (1150 in³), with a bore and stroke of 159 x 159 mm, turbocharged and aftercooled. Cummins publishes marine ratings of 373–597 kW (500–800 hp) across continuous, heavy duty and medium continuous ratings.

It is worth correcting a figure that circulates widely online: several parts retailers quote the QSK19 at 800–1,000 hp. Cummins' own published marine ratings top out at 800 hp. If you are sizing spares or assessing a repower against published figures, use the manufacturer's data.

Several design features distinguish the QSK19 and are directly relevant to maintenance planning. The single-loop cooling system removes the need for two keel coolers, reducing installation complexity. The engine-mounted titanium plate heat exchanger is more durable in corrosive seawater than conventional alternatives. The water-cooled exhaust manifold is a single-piece casting that eliminates a common leak path and reduces engine room surface temperatures. And the turbocharger is water-cooled and optimised for vessel operating conditions.

The engine is designed to meet International Association of Classification Societies (IACS) and SOLAS requirements, with class approvals available — which matters for any operator running classed tonnage.

What vessels use the QSK19?

The QSK19's power range and commercial-duty engineering place it across demanding marine sectors:

• Tugboats — a primary application, where torque characteristics handle towing loads that would overstress smaller engines
• Offshore supply and platform support vessels, where downtime carries significant operational cost
• Commercial ferries, as main propulsion on smaller vessels or within multi-engine installations
• Super yachts and yacht support vessels — Cummins markets the QSK19's commercial-duty reliability specifically for this sector
• Coastguard and naval patrol vessels requiring sustained performance under variable load
• Fishing and processing vessels, particularly larger trawlers working North Atlantic conditions
• Diesel-electric installations, where the QSK19 is available in a dedicated rating

What is the difference between the KTA19 and the QSK19?

The KTA19 uses Cummins' mechanical PT fuel system; the QSK19 uses the Modular Common Rail system with full electronic control via the CM850 ECM. The QSK19 meets IMO Tier II, EPA Tier 3 and EU Stage IIIa, with IMO III ratings also available — standards the older mechanical engine does not meet. The QSK19 also uses water-cooled exhaust and turbocharger arrangements where the KTA19 does not. Internally the QSK19 draws on the proven K19 block architecture, but the fuel, control and cooling systems differ substantially. They do not share fuel system parts and should not be treated as interchangeable for servicing.

What do the QSK19-M and QSK19-DM designations mean?

QSK19-M denotes the variable-speed propulsion rating. QSK19-DM denotes the fixed-speed auxiliary rating used for prime power generation at 1500 rpm (50 Hz) or 1800 rpm (60 Hz). Ratings, governor configuration and some ancillary components differ, so specify which you have.

Is the QSK19 suitable for recreational use?

Cummins markets the QSK19 for both commercial and recreational super yacht applications. Its commercial-grade engineering provides a reliability margin above engines designed primarily for leisure duty, which is why it appears in high-value yacht builds alongside its commercial fleet applications.

Which spare parts does the QSK19 most commonly need?

MCRS injectors and high-pressure fuel components

The Modular Common Rail system is the QSK19's greatest operational advantage and its most sensitive component group for sourcing. MCRS injectors are calibrated to the engine's ECM and must be matched to the specific CPL and rating — not simply the model. Unlike mechanical K-series injectors, they require compatibility with the engine's calibration data; unverified components create emissions non-compliance and combustion quality problems.

Turbocharger

The QSK19 uses a water-cooled turbocharger optimised for marine conditions, which reduces surface temperatures and fire risk but adds the turbo cooling circuit to the maintenance scope. In commercial propulsion duty the turbo sees aggressive load cycling — full boost departing port, sustained high load at sea, frequent spooling when manoeuvring in congested water. Correct specification requires the engine serial number and configuration data.

Piston-liner kits and overhaul components

The QSK19 uses a single-piece cast-iron ductile piston with nitride-coated rings running in a hardened cylinder liner — a combination designed for long intervals between overhauls in commercial service. When overhaul is due, CPL-specific selection of the piston-liner kit and full overhaul kit ensures the correct compression ratio and ring specification for the exact build.

Cylinder heads

QSK19 cylinder heads are precision components with valve seat and guide specifications tied to the engine's rating. In marine duty, thermal loading on the head is higher than on equivalent land-based applications of similar output, particularly in continuous high-load propulsion service. Heads should be pressure-tested before reuse.

Gaskets and seals, including exhaust manifold

A complete set covers head gaskets, exhaust manifold gaskets, oil seals throughout the engine and the fuel system O-ring set. The water-cooled single-piece exhaust manifold makes the manifold-to-head interface a critical sealing point — a leak there admits water to the exhaust path or exhaust gas to the cooling circuit, neither of which is recoverable without a strip.

Heat exchanger and cooling circuit components

The titanium plate heat exchanger is more durable than conventional alternatives but still requires periodic inspection for fouling and scale, particularly in coastal and harbour water with high biological loading. Raw water pump and cooling circuit components are standard maintenance items.

Sensors and CM850 ECM components

The CM850 ECM monitors all critical parameters and provides diagnostics, prognostics and complete engine protection, connecting to vessel systems through a simplified customer interface box. Sensor failures — oil pressure transducers, coolant temperature and speed sensors — trigger derate or shutdown responses that take the engine offline mid-operation. On commercial vessels where propulsion loss has serious consequences, holding verified spares for critical channels is standard practice.

How do you identify the correct QSK19 part?

The QSK19 is produced in multiple power ratings and to different emissions standards — including both IMO Tier II and IMO III variants of the same nominal output. The CPL number on the data plate determines the fuel system calibration, compression ratio and build specification, and therefore which parts are correct.

This matters most for MCRS injectors and turbochargers, where an incorrect variant will not perform correctly regardless of whether it physically fits.

What to send with your enquiry

Supplying the right information up front removes a round of questions and gets you a firm price faster. For any quote on this engine, please include:

Why source from AMS Parts

AMS Parts is a UK-based supplier of genuine and OEM spare parts for marine, power generation and industrial diesel engines. We verify every quotation against the engine serial number rather than leaving compatibility to the buyer, and we supply genuine and OEM parts only — we do not offer aftermarket components. Our full range of Cummins engine spare parts covers propulsion, auxiliary and generator applications, with worldwide shipping to vessels and service facilities.

Related guides

• Cummins KTA19-M marine engine spare parts
• Cummins QSM11 marine engine spare parts
• Cummins QSK engine series explained
• How to find the right Cummins part using your ESN