Detroit Diesel 6-71 Marine Engine Specifications (2 Valve, 4 Valve Non-Turbo & Turbo)

October 9, 2024

Everything You Need To Know About Detroit Diesel 6-71 Specifications

The Detroit Diesel 6-71 is a legendary engine from the Detroit Diesel 71 Series, well-regarded for its reliability, power, and versatility in a variety of marine applications. Known for its distinctive two-stroke sound, this engine has powered countless fishing vessels, tugboats, and offshore supply vessels over the years. The 6-71 is available in multiple configurations, including 2-valve and 4-valve versions, as well as non-turbo and turbocharged options. Below, we’ll explore the specifications and features of each configuration of the Detroit Diesel 6-71 marine engine.

 

Detroit Diesel 6-71 Marine Diesel Engine
A Pair Of Detroit Diesel 6-71 In A Tugboat (Owner Of The Boat Is Hempstead Marine)

Overview of the Detroit Diesel 6-71

The 6-71 engine is a 6-cylinder, inline engine with a displacement of 426 cubic inches (71 cubic inches per cylinder). This two-stroke engine utilizes a Roots-type blower for air intake, which is essential for efficient operation. Unlike four-stroke engines, the 6-71 relies on exhaust valves and intake ports in the cylinder walls, while the blower forces fresh air into the cylinders.

General Specifications Across All Configurations:

  • Configuration: 6-cylinder, inline
  • Displacement: 426 cubic inches (7.0 liters)
  • Bore and Stroke: 4.25 x 5.0 inches
  • Cooling System: Water-cooled
  • Weight: Approximately 2,300 – 2,700 lbs, depending on configuration
  • Fuel System: Mechanical unit injectors

Understanding the Two-Stroke Design

In two-stroke Detroit Diesel engines like the 6-71, intake air is supplied by a Roots-type blower and flows through intake ports, which the piston uncovers as it descends. This fresh intake air then pushes out the exhaust gases through the exhaust valves, which are the only valves present in the cylinder head. This process makes the 6-71 distinctive as it utilizes exhaust-only valves, with the blower supplying the intake air directly.

2-Valve Non-Turbo Specifications

The 2-valve non-turbocharged version of the Detroit Diesel 6-71 is known for its simplicity and dependable performance, making it suitable for moderate marine applications that don’t require the extra power from a turbocharger.

Specifications for the 2-Valve Non-Turbo:

  • Horsepower: Approximately 160-190 HP at 1,800 RPM
  • Torque: Around 485 lb-ft at 1,200 RPM
  • Aspiration: Naturally aspirated, with intake air provided by a Roots-type blower
  • Valvetrain: 2 exhaust valves per cylinder
  • Compression Ratio: 18.7:1

This configuration is ideal for smaller vessels that prioritize reliability and ease of maintenance. Its straightforward design allows for simple servicing, making it a durable choice for vessels operating in remote areas.

4-Valve Non-Turbo Specifications

The 4-valve non-turbo version features four exhaust valves per cylinder instead of two, which improves the exhaust flow, resulting in better overall efficiency. Like the 2-valve version, this configuration relies solely on the blower for intake air, with no turbocharger.

Specifications for the 4-Valve Non-Turbo:

  • Horsepower: Approximately 200-220 HP at 1,800 RPM
  • Torque: Around 500-525 lb-ft at 1,200 RPM
  • Aspiration: Naturally aspirated with a blower
  • Valvetrain: 4 exhaust valves per cylinder
  • Compression Ratio: 17.0:1

This setup provides a slight boost in performance over the 2-valve non-turbo version and is suited to applications requiring higher power without the added complexity of a turbocharger.

4-Valve Turbo Specifications

The 4-valve turbocharged configuration is the highest-performing option for the 6-71, utilizing both turbocharging and a blower to maximize power output. The turbocharger compresses the intake air, increasing oxygen levels and enabling more efficient combustion.

Specifications for the 4-Valve Turbo:

  • Horsepower: Approximately 300-335 HP at 2,100 RPM
  • Torque: Around 800 lb-ft at 1,200 RPM
  • Aspiration: Turbocharged with a Roots-type blower
  • Valvetrain: 4 exhaust valves per cylinder
  • Compression Ratio: 16.0:1

The turbocharged 4-valve version is designed for high-performance applications, delivering substantial horsepower and torque. This setup is ideal for larger vessels and applications that require maximum power and speed. Turbocharging increases air density, allowing the engine to burn more fuel efficiently and produce more power while maintaining fuel efficiency.

Choosing the Right Configuration for Your Needs

Each 6-71 configuration offers unique benefits based on the demands of your marine application:

  • 2-Valve Non-Turbo: Best for smaller vessels and applications that prioritize simplicity and low maintenance. Ideal for steady, moderate power requirements.
  • 4-Valve Non-Turbo: Provides a performance boost over the 2-valve non-turbo version, making it suited to vessels requiring additional power but not the complexity of a turbocharger.
  • 4-Valve Turbo: The ultimate choice for maximum horsepower and torque, perfect for large vessels and high-demand applications where reliability under heavy loads is critical.

Marine Applications: Powering the Seas

The Detroit Diesel 671 has long been used in various marine applications due to its durability and adaptability. Below are the typical vessel types and sizes that rely on the 671 engine:

  1. Commercial Fishing Boats: The 671 is commonly found in offshore fishing boats between 40-60 feet, offering the reliability needed for long trips in difficult conditions.
  2. Workboats: The 671, especially the turbocharged models, powers medium-sized workboats and utility vessels between 40-60 feet.
  3. Pleasure Yachts and Recreational Boats: The naturally aspirated version of the 671 is favored in pleasure yachts and recreational boats between 30-50 feet, providing a balance of smooth operation and fuel efficiency.
  4. Smaller Tugboats: For small harbor tugs and workboats, the 671 engine is used due to its reliability and steady power output for vessels in the 30-50 foot range.  Below is a video tour of Hempstead Marines tugboat fleet. One of their boats is powered by Detroit Diesel 6-71 Engines:

Aftermarket Support: Keeping the 671 Engine Running

With support from Diesel Pro Power, owners of the Detroit Diesel 671 can maintain and repair their engines with a wide range of aftermarket parts. Whether you have a 2-valve, 4-valve, or turbocharged engine, Diesel Pro Power provides the necessary components to keep these engines in top condition.

Below is a breakdown of the essential parts available for each engine configuration:

2-Valve Engine Support

Send A Free Troubleshooting Guide For The Detroit Diesel 671 2-Valve Engine To Yourself

For 2-valve Detroit Diesel 671 engines, typically used in smaller vessels (under 50 feet), Diesel Pro Power provides:

 

 

 

 

 

4-Valve Engine Support

Send A Free Troubleshooting Guide For The Detroit Diesel 671 4-Valve Non Turbo Engine To Yourself

For 4-valve Detroit Diesel 671 engines, typically used in medium-sized vessels up to 60 feet, Diesel Pro Power offers:

 

 

Turbocharged Engine Support

Send A Free Guide About Troubleshooting The Detroit Diesel 671 Turbo Engine To Yourself

For turbocharged Detroit Diesel 671 engines, typically found in larger vessels up to 60 feet, Diesel Pro Power offers:

 

Videos About The Detroit Diesel 671:

Installing The Camshaft & Timing Gears On A Detroit Diesel 671

Installing The Cylinder Head & Injectors On A Detroit Diesel 671

Installing Injectors & Fuel Lines For Detroit Diesel 671

Assembling a Detroit Diesel 6-71 Longblock Part 1

Assembling A Detroit Diesel 671 Longblock Part 2

The Detroit Diesel 6-71 continues to be a reliable power source for marine operators due to its durability and adaptability across various configurations. By choosing the right setup for your vessel, you can ensure that your 6-71 provides the power, efficiency, and longevity that Detroit Diesel engines are known for.

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