The Legacy of the Detroit Diesel Marine 671 Engine & Its Use Today

October 8, 2024

Everything You Need To Know About The Detroit Diesel 671

The Detroit Diesel 671 engine has become a staple in the marine industry, renowned for its reliability and versatility. This iconic engine has powered vessels for decades, particularly in commercial fishing boats, small workboats, and pleasure yachts. Known for its simple design and ruggedness, the 671 engine continues to be relevant in marine propulsion, with a lasting legacy in vessels ranging from 30 to 60 feet in length.

This retrospective explores the history, technical evolution, and the comprehensive aftermarket support offered by Diesel Pro Power to keep these engines in prime working condition, whether they are 2-valve, 4-valve, or turbocharged models.

Evolution: From 2-Valve to 4-Valve and Turbocharged Models

Transition from 2-Valve to 4-Valve Heads

The Detroit Diesel 671 originally featured a two-valve head, which was designed for smaller boats that required moderate power. As larger vessels and higher performance needs emerged, Detroit Diesel introduced a four-valve head version, which offered enhanced airflow and improved fuel efficiency.

Turbocharged Versions

Turbocharging brought even more power to the 671, making it suitable for more demanding marine applications. By forcing additional air into the combustion chamber, Detroit Diesel 671 turbocharged models could generate significantly more horsepower, ideal for heavier-duty vessels.

  • Naturally Aspirated Models: Produced 170 to 225 horsepower, suitable for boats ranging from 30 to 50 feet in length.
  • Turbocharged Models: Capable of producing up to 300 horsepower, suitable for 60-foot vessels, such as larger workboats or commercial fishing vessels.

In the Detroit Diesel 6-71 engine, turbocharging can be paired with either intercooling or aftercooling to improve power output, efficiency, and cooling. Here’s a breakdown of how turbocharging, intercooling, and aftercooling differ and the benefits they offer for the 6-71 engine:

1. Turbocharged Intercooled 671 Engines

In a turbocharged intercooled engine, the intercooler (also known as a charge air cooler) is placed between the turbocharger and the engine intake manifold. The intercooler cools the compressed air coming from the turbo before it reaches the engine. By cooling the air before it enters the combustion chamber, the intercooler helps:

  • Increase Air Density: Cooling the air makes it denser, allowing for more oxygen to be packed into the engine for combustion. This results in better performance and more efficient fuel combustion.
  • Reduce Engine Temperature: Intercooling can help lower engine temperatures by reducing the intake air temperature. This helps prevent engine overheating, particularly during extended periods of high power output.
  • Improved Power and Efficiency: By providing denser air for combustion, an intercooled turbo setup increases overall horsepower and can improve fuel efficiency.

2. Turbocharged Aftercooled 671 Engines

In a turbocharged aftercooled engine, the aftercooler is placed after the compressed air has gone through the engine’s intake manifold and before it reaches the combustion chambers. This placement allows the aftercooler to further reduce air temperatures after compression. Aftercooling offers similar benefits to intercooling but is specifically positioned to handle additional cooling after air has moved through more components. The main advantages include:

  • Greater Cooling Capacity: Aftercoolers provide cooling at a later stage, which can be particularly helpful in high-load applications where the engine operates at higher temperatures. This setup is ideal for marine engines that need additional cooling to handle sustained high power output.
  • Enhanced Durability: By lowering temperatures further downstream, aftercooling can help protect engine components from the heat-related wear and stress caused by prolonged operation.
  • Better Fuel Economy and Emissions Control: Aftercooled engines can more completely burn fuel, which can lead to better fuel economy and lower emissions due to a reduction in unburned fuel particles.

Key Differences Between Intercooled and Aftercooled Systems

While both intercooling and aftercooling serve the purpose of reducing intake air temperature, they differ in terms of positioning and specific benefits:

  • Positioning: Intercoolers are placed between the turbo and the intake manifold, while aftercoolers are positioned closer to the engine cylinders, usually after the intake manifold.
  • Cooling Efficiency: Aftercoolers generally provide greater cooling since they cool air closer to the combustion chamber, which can be advantageous in extreme marine environments.
  • Usage: Intercoolers are more commonly found in applications where reducing intake air temperature before it enters the intake manifold is enough to optimize combustion, while aftercoolers are used when additional cooling is necessary closer to combustion.

For the Detroit Diesel 6-71, the choice between turbocharging with intercooling or aftercooling depends on the specific needs of the application. For extended heavy-duty marine operations, aftercooling is often preferred due to its enhanced cooling capacity and ability to better handle high-power demands.

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

Conclusion

The Detroit Diesel 671 engine is a maritime icon, trusted by boat owners for its reliability and durability across a wide range of vessels, including 30-60 foot fishing boats, workboats, and pleasure yachts. Its adaptability, whether in naturally aspirated, 4-valve, or turbocharged configurations, has allowed it to maintain its place in the marine industry for decades.

For high-quality aftermarket parts, including overhaul kits, turbochargers, injectors, pumps, and more, visit **The Detroit Diesel 671 engine remains a highly regarded and versatile powerplant, trusted by boat operators worldwide for its reliability, ruggedness, and ease of maintenance. Commonly used in 30-60 foot vessels like commercial fishing boats, workboats, and pleasure craft, its simple design and wide range of configurations — from 2-valve, 4-valve, to turbocharged models — continue to serve marine applications with consistent performance.

For aftermarket support and to find the necessary parts to keep your Detroit Diesel 671 running strong, visit Diesel Pro Power. The company offers everything you need, including overhaul kits, injectors, freshwater pumps, raw water pumps, cylinder heads, oil pumps, crankshafts, camshafts, and turbochargers tailored to each configuration.

 

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