Searching for a Cummins QSB 6.7 marine engine for sale? Whether you’re replacing an aging engine, repowering a fishing boat, or sourcing a diesel engine for a commercial vessel, the goal is the same: find an engine that matches your boat, your operating requirements, and your budget without creating expensive problems after delivery.
The Cummins QSB6.7 is a turbocharged, aftercooled, six-cylinder marine diesel engine family designed for recreational and commercial marine applications. Depending on the specific model and rating, it offers different power outputs for different operating demands. Cummins publishes recreational propulsion ratings ranging from 250 MHP to 550 MHP, along with separate commercial and light-duty marine ratings. These ratings are not interchangeable, so choosing the correct configuration is essential.
At Power Engine Market, the most useful starting point for a buyer is not simply the advertised horsepower or price. It is understanding exactly which engine is being offered, what your vessel requires, what is included in the sale, and which details still need to be confirmed.
This guide walks you through Cummins QSB 6.7 marine engine specifications, horsepower ratings, boat repower considerations, transmission compatibility, used-engine inspections, pricing factors, and shipping questions. The aim is to help you make a more informed purchasing decision before committing your money.
What Is the Cummins QSB 6.7 Marine Engine?
The Cummins QSB6.7 is a 6.7-liter, inline six-cylinder, four-stroke diesel engine with turbocharging, aftercooling, and a high-pressure common-rail fuel system. It is designed for marine applications where the selected engine rating and installation are appropriate for the vessel.
The QSB6.7 name identifies an engine family, not one universal engine package. Different ratings, configurations, and intended operating profiles can affect the engine’s output, installation requirements, and suitability for a particular boat.
For buyers searching for a Cummins QSB 6.7 marine diesel engine for sale, this distinction matters. Two listings may both mention QSB6.7 while describing engines with different rated outputs, accessories, condition, or intended service.
Before comparing prices, establish the exact model designation and rating of each engine you are considering.
Where Is the QSB6.7 Used?
The QSB6.7 family covers recreational and commercial marine propulsion applications. Depending on the exact model and rating, it may be relevant to projects involving:
- Recreational boats and cruising vessels.
- Fishing boats and working vessels.
- Commercial marine propulsion.
- Eligible marine repowering projects.
- Other applications approved for the particular engine configuration.
The intended operating profile is especially important. A boat used for occasional leisure trips may have different requirements from a commercial vessel that spends long hours operating under load.
An engine’s horsepower rating alone does not tell you whether it is suitable for continuous or demanding commercial operation. Check the manufacturer’s rating classification and match it to the vessel’s actual duty cycle.
Why the Exact Model and Serial Number Matter
When a seller advertises a QSB6.7, ask for the exact model designation and engine serial number. These details help identify the particular engine and provide a starting point for verifying its specifications, configuration, service information, and parts requirements.
This is particularly useful when considering a used engine or replacing an existing unit. A family name and a horsepower figure are not enough to establish that the engine will fit your boat or work with your existing transmission.
If a listing does not provide these details, request them before treating the offer as a confirmed match.
Cummins QSB 6.7 Marine Engine Specifications
Technical specifications are useful when comparing engines, but they must be interpreted in context. The dimensions and ratings below are published for the Cummins QSB6.7/QSB7 marine family. They are general reference figures, not a substitute for documentation covering the specific engine being offered.
| Specification | Published information |
|---|---|
| Engine configuration | Inline six-cylinder, four-stroke diesel |
| Displacement | 6.7 L (408 in³) |
| Aspiration | Turbocharged and aftercooled |
| Fuel system | High-pressure common rail |
| Bore and stroke | 107 × 124 mm (4.21 × 4.88 in) |
| Rotation | Counterclockwise when facing the flywheel |
| Overall length | Approximately 49.76 in (1,263.8 mm) |
| Overall width | Approximately 35.85 in (910.6 mm) |
| Overall height | Approximately 33.74 in (857 mm) |
| Published weight | Approximately 1,450 lb (658 kg) |
Technical note: Cummins states that dimensions and weight can vary according to the selected engine configuration. Some versions or packages may have different installation requirements. Always request the applicable technical drawing and verify the details for the exact engine you intend to purchase.
For the manufacturer’s specifications and ratings, consult the official Cummins QSB6.7/QSB7 marine engine page.
How Much Horsepower Does the Cummins QSB 6.7 Produce?
Cummins publishes several recreational marine propulsion ratings for the QSB6.7 family. Examples include:
| Recreational marine rating | Published engine speed |
|---|---|
| 250 MHP | 2,600 RPM |
| 305 MHP | 2,600 RPM |
| 355 MHP | 3,000 RPM |
| 380 MHP | 3,000 RPM |
| 425 MHP | 3,000 RPM |
| 480 MHP | 3,300 RPM |
| 550 MHP | 3,300 RPM |
These are examples of published recreational propulsion ratings. Cummins also lists separate commercial and light-duty marine propulsion ratings, with different rating classifications and, in some cases, different engine speeds.
Notice that the table uses MHP, not BHP. Cummins’ published figures show that these units can have different numerical values for the same rating. When comparing engine listings, check the unit, rated speed, exact model, and rating classification rather than assuming every horsepower figure means the same thing.
For a closer review of published ratings and technical details, consult the Cummins QSB6.7 marine engine technical brochure
Why More Horsepower Is Not Always Better
It is easy to focus on the largest horsepower number when shopping for a marine engine. However, an engine must be appropriate for the boat and propulsion system.
Consider a repower project where the existing engine is no longer serviceable. A replacement with a higher advertised output may look attractive, but the boat’s hull, drivetrain, cooling system, exhaust, and manufacturer-approved power range all need to be considered.
The correct engine is the one that meets the vessel’s requirements—not necessarily the one with the highest number on the specification sheet.
For commercial use, rating classification is particularly important. Do not assume a recreational high-output rating is suitable for a vessel that operates under sustained commercial loads. Confirm the intended application with the manufacturer or a qualified marine professional.
Is the Cummins QSB 6.7 Right for Your Boat?
Before buying a Cummins QSB 6.7 engine for boat repower, start with how the boat is used, how it is configured, and what you need the replacement engine to accomplish.
For Recreational Boats and Cruisers
Recreational owners may prioritize cruising performance, comfortable operation, reliable propulsion, and manageable servicing requirements.
The right QSB6.7 configuration depends on the vessel’s design, displacement, propulsion arrangement, and approved power range. It is also worth considering whether the engine compartment allows access for routine maintenance and whether suitable technical support is available where the boat operates.
Do not choose the rating based only on a desired top speed. Ask a marine professional to evaluate the complete installation and propulsion requirements.
For Fishing Boats and Commercial Vessels
Commercial operators often have to consider downtime, operating schedules, payload, and maintenance planning. An unsuitable engine choice can affect more than performance: it can create additional installation work or leave the vessel poorly matched to its intended duty.
If the boat operates for extended periods under load, explain this clearly when requesting an engine quotation. Ask which specific model and rating are appropriate for that operating profile.
The distinction between intermittent, heavy-duty, and continuous or medium-continuous ratings—where applicable—is not just a label. It helps define the operating conditions for which an engine rating is intended. The exact rating definitions and limitations should be checked in the manufacturer’s documentation.
For Marine Repowering Projects
Repowering means replacing an existing engine with another engine while retaining some or all of the boat’s existing systems. It can be a practical route when an old engine is beyond economical repair, but the work can involve more than swapping one engine for another.
For example, imagine that a boat owner finds a QSB6.7 with an attractive price and a horsepower rating that appears suitable. Once the installation is measured, the owner discovers that the gearbox arrangement, mounts, or exhaust routing needs further work. The original price may still be competitive, but the full project cost has changed.
This is a common type of issue to plan for in any repower project. It is not a claim about a specific Power Engine Market customer; it illustrates why compatibility should be checked before purchase.
A pre-purchase review by a qualified marine technician can help identify these requirements before the engine is ordered.
How to Check Cummins QSB 6.7 Marine Engine Compatibility
An engine that does not fit the vessel’s installation or cannot be matched to the propulsion system can create costly delays. Use the following checks to evaluate a proposed replacement.
1. Measure the Engine Compartment
Start with the available space. Compare the engine’s published dimensions with the engine compartment, but do not stop at length, width, and height.
You also need to consider access for servicing, lifting and removal, filters, hoses, electrical connections, and any attached transmission. A unit may physically fit inside a compartment while still leaving insufficient room to maintain it properly.
Ask for the dimensional drawing for the exact engine configuration. General family dimensions are helpful for preliminary screening, but they should not be used as final installation approval.
2. Check the Mounts and Shaft Alignment
Engine mounts support the engine and help control vibration. Their positions and suitability must be reviewed when replacing an engine.
For shaft-driven boats, the engine and gearbox also need to align correctly with the propulsion shaft. Incorrect alignment can contribute to vibration, premature component wear, and mechanical problems.
Do not assume the original mounts or shaft arrangement will work without modification. Have a qualified marine technician check the proposed installation and identify any work required.
3. Confirm Cummins QSB 6.7 Gearbox Compatibility
When assessing Cummins QSB 6.7 gearbox compatibility, confirm the exact transmission model and the requirements of the proposed engine.
Important details include:
- Transmission input-power and torque ratings.
- Gear ratio and intended operating speed.
- Rotation requirements.
- Bellhousing, adapter, and mounting arrangement.
- Coupling and shaft configuration.
- Any manufacturer restrictions on the proposed combination.
The transmission affects how engine power is delivered to the propeller. A gearbox should not be selected solely because it physically attaches to the engine.
If you plan to reuse the existing transmission, provide its identification plate details to the supplier and installation professional. Ask them to confirm that the proposed combination is appropriate before placing the order.
4. Review Cooling, Exhaust, Fuel, and Electrical Systems
Marine engine installations depend on the surrounding systems as well as the engine itself.
Check the cooling arrangement, fuel supply and filtration, exhaust routing, electrical connections, engine controls, and monitoring instruments. Depending on the existing boat and the replacement configuration, some components may be reusable while others may need adaptation or replacement.
Electronic controls and instrumentation deserve particular attention. Do not assume that an older boat’s wiring or control system will automatically work with the replacement engine.
Have the installation requirements reviewed by a qualified professional who can identify what needs to be retained, changed, or replaced.
5. Verify the Propeller and Operating Range
The engine, gearbox, shaft, and propeller need to operate as a compatible system. Propeller selection depends on the boat’s design, reduction ratio, operating conditions, and required performance.
An unsuitable propeller setup can prevent an engine from reaching its specified operating range or place excessive load on the drivetrain. The correct choice should be established through the appropriate technical assessment—not guesswork.
Buying a New or Used Cummins QSB 6.7 Marine Engine
A new engine and a used engine can serve different purchasing needs. The better option depends on the specific unit, its documentation, your budget, and your tolerance for uncertainty.
What to Verify When Buying a New Engine
If you are considering a new Cummins QSB 6.7 marine engine for sale, verify the exact model and rating, condition, included components, supply arrangements, and applicable warranty terms.
Ask the seller to specify whether the offer includes items such as the transmission, controls, wiring, instruments, mounting hardware, and other accessories. Do not assume the quoted engine is a complete ready-to-install package unless the offer says so.
You should also confirm the expected dispatch timeframe, shipping method, and delivery estimate. These details should be specific to the engine and destination rather than assumed from a general listing.
What to Check When Buying a Used Cummins QSB 6.7
A used Cummins QSB 6.7 marine engine may suit a project where budget or availability is a major consideration. However, a used engine should be assessed on its condition and supporting evidence—not appearance alone.
Request the engine serial number, service history, available operating-hour information, repair records, and any inspection or test reports. Ask whether the engine has been removed from a working vessel, stored for a period, rebuilt, or modified.
Where possible, arrange an inspection by a qualified marine diesel technician. Depending on the engine’s condition and access, the inspection may include:
- Checking for visible damage, leaks, corrosion, or signs of poor storage.
- Reviewing diagnostic information where available.
- Inspecting fluid condition and maintenance evidence.
- Checking the fuel and cooling systems as appropriate.
- Conducting suitable mechanical tests.
- Running the engine under safe, appropriate conditions if this is possible and authorized.
No single visual check or brief start-up can establish the full condition of a used engine. A professional assessment should be appropriate to the engine’s condition and the risks involved.
Also request clear photographs of the identification plate and the actual unit being offered. Make sure the serial number and configuration information match the sales documentation.
Questions to Ask the Seller
Before committing, ask:
- What is the exact engine model and serial number?
- What is the rated output, RPM, and application rating?
- Is the engine new, used, rebuilt, or remanufactured?
- What components and accessories are included?
- Are service records, inspection results, or test reports available?
- What warranty terms apply to this specific engine, if any?
- What are the confirmed engine price and shipping costs?
- What are the estimated dispatch and transit times?
- What happens if the delivered engine does not match the agreed description or arrives damaged?
Clear answers make it easier to compare offers fairly and establish the terms of the transaction.
Cummins QSB 6.7 Marine Engine Price: What Determines the Cost?
The Cummins QSB 6.7 marine engine price depends on the exact engine being offered. Condition, rating, configuration, included equipment, and seller terms can all affect the price.
A used engine with documented service history is not directly comparable to a new engine supplied in a different configuration. Before deciding that one offer is cheaper, compare what is actually included.
Engine Condition and Configuration
New, used, rebuilt, and remanufactured engines may have different prices and warranty arrangements. The specific rating and configuration also matter.
Check whether the quoted engine is the model you need and whether its condition has been clearly documented. A low advertised price is not necessarily the best value if the engine requires substantial repairs or additional components.
Accessories and Installation Costs
Confirm whether the quote includes the gearbox, controls, wiring harness, instrumentation, mounts, and other required items.
Installation costs may include lifting equipment, labor, shaft work, alignment, cooling and exhaust modifications, and commissioning. The amount varies by vessel and existing installation, so obtain a project-specific estimate rather than relying on a generic figure.
Shipping and Handling
The cost of Cummins QSB 6.7 marine engine shipping depends on factors such as the origin, destination, weight, dimensions, packaging, carrier, and delivery arrangements.
Before approving the purchase, request a written quotation showing:
- Engine price.
- Shipping fee.
- Shipping method.
- Estimated dispatch timeframe.
- Estimated transit time.
- Any confirmed destination charges, duties, or taxes relevant to the transaction.
If any amount or timeframe is not yet confirmed, it should be identified as pending—not presented as a guaranteed cost or delivery date.
Compare the Total Project Cost
The engine’s purchase price is only one part of the investment. Add the cost of any necessary accessories, freight, installation, commissioning, and vessel modifications. Also consider the maintenance and service requirements associated with the engine’s condition and operating profile.
A more expensive engine may be the better choice if it is the correct configuration and comes with stronger documentation. Conversely, paying more does not automatically guarantee better condition or suitability. Compare the actual evidence and terms behind each offer.
Shipping a Cummins QSB 6.7 Marine Engine
Marine engines are heavy, valuable items that may require specialist freight handling. If you are sourcing an engine from another state or country, establish the shipping arrangements before paying.
Provide the supplier with your delivery destination and explain any receiving limitations. For example, confirm whether delivery is required to a business address, freight terminal, port, or another location, and whether suitable equipment will be available to unload the shipment.
Depending on the route and destination, the transaction may also involve customs documentation, import duties, taxes, or other charges. Responsibility for these items should be stated clearly in the quotation.
Confirm the Timeline in Writing
A useful shipping estimate distinguishes between preparation time, dispatch, and transit. An engine that is ready for shipment may have a different timeline from one that requires inspection, preparation, or sourcing.
Ask the supplier to state what is confirmed and what remains an estimate. Do not assume that an advertised availability statement means the engine can be dispatched immediately.
Before shipment, verify the delivery address, packaging arrangements, shipping method, expected timeline, and process for reporting transit damage or discrepancies.
Maintenance and Long-Term Ownership
Buying the engine is only the beginning. Before choosing a Cummins QSB 6.7 marine diesel engine for sale, consider whether you can obtain appropriate maintenance support and technical information for the specific model.
Cummins identifies a global service network as part of its support offering. However, the availability of specific services, parts, and qualified technicians depends on the location and engine configuration. Check the options available where your vessel will operate.
Follow the Correct Service Schedule
Use the maintenance schedule and service instructions that apply to the exact engine model and rating. Routine maintenance may involve engine oil and filters, fuel filtration, cooling-system checks, belts and hoses, and other model-specific items.
Do not rely on a generic schedule without checking the manufacturer’s guidance. Service requirements can depend on operating hours, duty cycle, environment, and the condition of the engine.
Keep records of completed maintenance, repairs, parts, and inspections. These records can help technicians understand the engine’s history and may be useful if you later sell it.
Watch for Changes in Operation
Pay attention to the operating indicators and warnings specified for the engine. Changes in starting behavior, temperature, oil pressure, vibration, exhaust appearance, or performance should be investigated rather than ignored.
If a warning appears or the engine behaves abnormally, follow the applicable operating instructions and seek qualified technical advice. Avoid assuming that continuing to operate the engine will resolve the issue.
Plan for Service and Parts Access
If your vessel operates far from major service centers, access to parts and qualified support deserves particular attention. Before purchasing, investigate how you would obtain routine service items and technical assistance for the exact model.
A suitable engine is one you can operate and maintain responsibly—not simply one that fits the available space.
Buying Through Power Engine Market: What to Confirm
Power Engine Market helps buyers explore engine purchasing options for their projects. If you are looking for a Cummins QSB 6.7 marine engine for sale, prepare the information needed to identify the right configuration and obtain a clear quotation.
Start by explaining whether you need a replacement engine, are planning a repower, or are sourcing an engine for another approved application. Share the boat’s make and model, current engine details, desired output, transmission information, and delivery destination.
If you are replacing an existing QSB6.7, include the engine identification details where possible. If you are moving from another engine family, provide the existing specifications and have a marine professional review the proposed replacement.
A reliable purchasing process should make the important details clear before payment. For the specific engine being quoted, confirm:
- Exact model, serial number, and rating.
- New or used condition and supporting documentation.
- Included components and accessories.
- Price and applicable warranty terms.
- Compatibility questions that still need technical approval.
- Shipping method, fee, and estimated delivery timeline.
Availability, condition, price, warranty, and shipping arrangements must be verified for the actual unit being offered. Do not assume that a particular rating is in stock or that a particular accessory is included unless the seller confirms it.
How to Request a Quote for a Cummins QSB 6.7 Marine Engine
A complete quotation request helps the supplier understand your requirements and reduces avoidable back-and-forth.
Information to Include
When contacting Power Engine Market, provide as many of the following details as you have:
- Engine family and model: Cummins QSB6.7, including the exact model designation if known.
- Required rating: Your target output and the application for which the engine is needed.
- Vessel details: Boat make, model, type, and relevant installation information.
- Current engine: Manufacturer, model, serial number, and rated output, if applicable.
- Transmission: Gearbox or transmission model if you intend to reuse it.
- Condition preference: New, used, rebuilt, or remanufactured.
- Delivery destination: City, region, and country.
- Timeline: When you need the engine delivered.
- Included equipment: Controls, transmission, accessories, or installation components you want quoted.
It is fine if you do not know every technical detail. Share the information available and identify the items that need professional confirmation.
Review the Quotation Before Paying
Check that the written offer identifies the specific engine and clearly states its condition, included components, price, warranty terms if applicable, and shipping arrangements.
If the quote does not answer a critical question—such as gearbox compatibility, the exact rating, or the total freight cost—ask for clarification before proceeding.
This final review is a simple way to reduce uncertainty and make sure both parties understand what has been agreed.
Frequently Asked Questions
What is the displacement of the Cummins QSB 6.7 marine engine?
The published displacement is 6.7 liters (408 cubic inches). The marine engine family uses an inline six-cylinder, four-stroke diesel configuration with turbocharging, aftercooling, and a high-pressure common-rail fuel system. Confirm the exact specifications for the particular engine being offered.
How much horsepower does the Cummins QSB 6.7 marine engine produce?
Cummins lists recreational marine propulsion ratings from 250 MHP to 550 MHP for the QSB6.7 family. Separate commercial and light-duty marine ratings are also available in the manufacturer’s published information. The correct rating depends on the exact configuration and intended application.
Is the Cummins QSB 6.7 suitable for a commercial fishing boat?
It may be suitable for certain commercial applications when the specific model and rating match the vessel’s requirements. Confirm the duty classification, operating profile, installation compatibility, and applicable regulatory requirements before buying.
Can I replace my current marine engine with a Cummins QSB 6.7?
Possibly. The proposed engine must be checked against the vessel’s available space, mounts, transmission, shaft alignment, cooling and exhaust systems, fuel supply, and controls. A qualified marine technician should assess the installation before you commit to the purchase.
What are the dimensions of the Cummins QSB 6.7 marine engine?
Cummins publishes general dimensions of approximately 49.76 inches long, 35.85 inches wide, and 33.74 inches high, with a listed weight of approximately 1,450 pounds. The manufacturer notes that dimensions and weight can vary by configuration. Request the correct drawing for your engine before planning the installation.
Is a used Cummins QSB 6.7 marine engine worth buying?
A used engine may suit your budget and project, but the decision should be based on its condition, documentation, model, and configuration. Request the serial number, service records, operating-hour information, and available inspection reports. Where possible, arrange a qualified inspection before purchase.
What affects the price of a Cummins QSB 6.7 marine engine?
The price depends on condition, rating, configuration, included equipment, and seller terms. Shipping, installation, commissioning, and vessel modifications also affect the total project cost. Request a quotation for the exact unit rather than relying on a generic estimate.
Does the Cummins QSB 6.7 come with a gearbox?
Do not assume that a gearbox is included. Ask the seller to identify every component covered by the offer. If you plan to reuse an existing transmission, have its suitability confirmed for the exact engine rating and installation.
How can I arrange shipping for a Cummins QSB 6.7 marine engine?
Provide your delivery destination and receiving requirements when requesting a quotation. Ask for the shipping method, confirmed freight cost, estimated dispatch timeframe, transit time, and any relevant destination charges. The actual arrangements depend on the shipment and route.
Where can I verify official Cummins QSB6.7 specifications?
Review the manufacturer’s official Cummins QSB6.7/QSB7 marine engine page. Use the documentation for the exact model and rating when checking specifications, dimensions, output, and intended applications.
Final Thoughts: Buy the Right Configuration, Not Just the Right Price
Finding a Cummins QSB 6.7 marine engine for sale is the first step. Making sure it suits your boat is what protects the value of the purchase.
Verify the exact model and rating. Check the installation dimensions, transmission arrangement, and propulsion requirements. If you are considering a used engine, review its history and condition carefully. Before paying, confirm what is included, which warranty terms apply, and how shipping will be handled.
A careful review before ordering can help you avoid compatibility surprises, unexpected costs, and preventable delays.
If you’re planning a marine repower or sourcing a replacement diesel engine, contact Power Engine Market with your engine requirements and delivery destination. Request a quotation for the specific Cummins QSB6.7 configuration you need, and have the proposed installation verified by a qualified marine professional before finalizing your purchase.
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