Cummins QSB6.7 355 HP Marine Diesel Engine
The Cummins QSB6.7 355 HP Marine Diesel Engine is a 6.7-litre, inline six-cylinder propulsion engine designed for recreational marine applications. Rated at 261 kW / 355 MHP (350 BHP) at 3,000 rpm, it combines turbocharging, aftercooling and High-Pressure Common Rail fuel injection in a compact marine diesel platform.
Designed for compatible powerboats, motor yachts and repower applications, the QSB6.7 offers substantial propulsion output while retaining the practical dimensions and installation characteristics of Cummins’ 6.7-litre engine family.
Overview
The Cummins QSB6.7 is built around an inline six-cylinder, four-stroke diesel configuration with a total displacement of 6.7 litres (408 in³).
In this recreational high-output configuration, the engine develops 261 kW / 355 MHP, equivalent to 350 BHP, at 3,000 rpm.
The engine combines turbocharged and aftercooled aspiration with Cummins High-Pressure Common Rail fuel technology. This provides a modern diesel propulsion platform for vessels requiring substantial power without moving to a considerably larger displacement engine.
Its six-cylinder architecture and compact overall package make the QSB6.7 particularly relevant where propulsion output, engine-room space and installation weight all need to be considered.
Applications and Compatibility
The Cummins QSB6.7 marine engine can be considered for compatible recreational marine vessels requiring propulsion in the 355 MHP class.
Potential applications include suitable powerboats, motor yachts and other recreational vessels, as well as repower projects where an existing marine diesel engine is being replaced.
For repowering, matching the horsepower of the existing engine is only the starting point.
Transmission and reduction ratio, propeller specification, shaft arrangement, engine mounts, available engine-room space, cooling, exhaust, electrical systems and controls should all be evaluated before confirming compatibility.
This becomes especially important when replacing an engine from another manufacturer. Two marine engines can have similar horsepower ratings while differing considerably in dimensions, weight and installation requirements.
Customers considering alternative outputs can also compare other Cummins marine engines and related marine diesel propulsion options to determine which configuration best matches their vessel.
Engine Design and Performance
At the centre of the QSB6.7 is a 6.7L inline six-cylinder diesel engine with a bore and stroke of 107 × 124 mm (4.21 × 4.88 in).
The engine uses a four-stroke operating cycle and turbocharged/aftercooled aspiration.
Turbocharging supplies the increased airflow required for the engine’s output, while aftercooling reduces the temperature of the compressed intake air before it reaches the cylinders.
This configuration allows Cummins to produce substantial marine propulsion power from the 6.7-litre platform.
For this recreational configuration, maximum rated output is 355 MHP at 3,000 rpm.
The distinction between horsepower measurements is worth noting when comparing specifications. Cummins identifies this rating as 355 MHP (metric horsepower), while the corresponding brake horsepower rating is 350 BHP.
High-Pressure Common Rail Fuel System
The QSB6.7 incorporates a High-Pressure Common Rail (HPCR) fuel system.
Common-rail technology separates the creation of fuel pressure from individual injection events, allowing electronically controlled fuel delivery according to engine operating requirements.
For buyers comparing the QSB6.7 with older mechanically injected marine engines, the HPCR system is one of the engine’s most significant technological differences.
It works alongside the engine’s turbocharging and aftercooling systems as part of the complete combustion and engine-management architecture.
For repower applications, the electronic nature of the engine should also be considered when evaluating controls, instrumentation, wiring and other vessel systems.
Installation and Dimensions
Physical size is particularly important when selecting a marine diesel engine.
The Cummins QSB6.7 has an overall published length of approximately 1,263.8 mm (49.76 in) and a block length of approximately 748 mm (29.45 in).
Overall width is approximately 910.6 mm (35.85 in), while height is approximately 857 mm (33.74 in).
Published engine weight is approximately 658 kg (1,450 lb).
These figures provide buyers with a useful starting point for assessing engine-room compatibility, particularly during a repower.
However, dimensions can vary according to the selected engine configuration. Adequate installation clearance must also be considered for servicing, cooling connections, exhaust, electrical systems and associated propulsion equipment.
Who Is This Engine Suitable For?
The Cummins QSB6.7 355 is particularly relevant to buyers requiring a six-cylinder marine diesel engine in the 355 MHP class for a compatible recreational vessel.
Potential buyers include boat owners, boatbuilders, marine workshops, engineers and repower specialists looking for a Cummins propulsion platform with 6.7 litres of displacement.
It may be particularly suitable for projects where substantial propulsion output is required while engine size and weight remain important considerations.
For repower installations, the QSB6.7 should be evaluated as part of the entire propulsion system rather than simply as a replacement based on horsepower.
Transmission compatibility, reduction ratio, propeller requirements, mounting points, cooling, exhaust, electrical integration and engine-room dimensions should all be confirmed before purchase.
Technical Specifications
For quick comparison, the principal specifications of the Cummins QSB6.7 355 HP Marine Diesel Engine are summarized below.
| Specification | Details |
|---|---|
| Manufacturer | Cummins |
| Model | QSB6.7 |
| Product Type | Marine propulsion diesel engine |
| Configuration | Inline 6-cylinder, 4-stroke diesel |
| Rated Output | 261 kW / 355 MHP / 350 BHP |
| Rated Speed | 3,000 rpm |
| Displacement | 6.7 L (408 in³) |
| Aspiration | Turbocharged / Aftercooled |
| Bore × Stroke | 107 × 124 mm (4.21 × 4.88 in) |
| Fuel System | High-Pressure Common Rail (HPCR) |
| Crankshaft Rotation | Counterclockwise facing flywheel |
| Overall Length | 1,263.8 mm (49.76 in) |
| Block Length | 748 mm (29.45 in) |
| Overall Width | 910.6 mm (35.85 in) |
| Overall Height | 857 mm (33.74 in) |
| Published Weight | 658 kg (1,450 lb) |
| Rating | High Output – Recreational |
| Emissions | IMO 2 / EPA 3 / RCD 2 |
| Primary Application | Recreational marine propulsion |
Dimensions and weight can vary depending on the selected engine configuration. Final installation requirements should be confirmed before purchase.
Ordering and Support
Before ordering the Cummins QSB6.7 355 HP Marine Diesel Engine, buyers should confirm the exact engine configuration and its suitability for their vessel.
For a repower, useful information includes the existing engine model, transmission, reduction ratio, propeller specification, engine-room dimensions and vessel type.
These details help establish whether the QSB6.7 can be integrated with the existing propulsion arrangement or whether modifications may be necessary.
Buyers should also confirm exactly what equipment is included with the engine being offered, particularly transmission, controls, instrumentation and installation accessories where applicable.
Customers requiring a different power rating can explore our Cummins marine engines range and related marine diesel engines to compare other propulsion options.
For current availability and configuration information, contact JB Marine GmbH with your vessel and engine requirements.
Frequently Asked Questions
How much power does the Cummins QSB6.7 355 produce?
The recreational QSB6.7 configuration produces 261 kW / 355 MHP (350 BHP) at 3,000 rpm. Cummins classifies this configuration as a high-output recreational marine propulsion rating.
What is the displacement of the Cummins QSB6.7?
The QSB6.7 has a displacement of 6.7 litres (408 in³). It uses an inline six-cylinder, four-stroke configuration with a 107 mm bore and 124 mm stroke.
Is the Cummins QSB6.7 turbocharged?
Yes. The QSB6.7 uses turbocharged and aftercooled aspiration. Turbocharging increases intake airflow, while aftercooling manages the temperature of the compressed air before it enters the engine.
Does the Cummins QSB6.7 use common-rail fuel injection?
Yes. The engine uses Cummins High-Pressure Common Rail (HPCR) fuel technology. This electronically controlled system manages high-pressure fuel delivery according to engine operating requirements.
How much does the Cummins QSB6.7 weigh?
Cummins publishes a weight of approximately 658 kg (1,450 lb) for the QSB6.7. Actual dimensions and weight can vary depending on the selected engine configuration, so the exact package should be confirmed before installation.
What are the dimensions of the Cummins QSB6.7?
Published dimensions are approximately 1,263.8 mm long, 910.6 mm wide and 857 mm high, with a block length of 748 mm. Installation clearance for servicing and associated equipment should also be considered.
Can the Cummins QSB6.7 355 be used for a repower?
The QSB6.7 can be considered for a compatible marine repower project. Suitability depends on transmission and reduction ratio, propeller requirements, engine mounts, available space, cooling, exhaust, controls and electrical integration rather than horsepower alone.
