Detroit Diesel Marine Long Blocks – 6-71 Natural & 8V71 Natural

Marine Long Blocks for Classic Detroit Diesel Engines

When a marine engine reaches the end of its service life, the fastest path back to dependable power is often through a long block replacement. For Detroit Diesel two-stroke engines, especially the 6-71 Natural and 8V71 Natural, long blocks provide a proven solution for commercial operators and vessel owners worldwide.

A marine long block is the core of your engine rebuilt to factory specification. It includes the block, crankshaft, connecting rods, pistons, camshaft, and cylinder heads—all precisely assembled to OEM standards. By starting with a fresh long block, you eliminate uncertainty, reduce downtime, and ensure your vessel is powered by an engine foundation you can trust.

Diesel Pro Power supplies long blocks trusted by 40,000+ customers in 180+ countries, helping fleets, shipyards, and independent operators keep their vessels running efficiently.

Detroit Diesel 6-71 Natural Marine Long Block

Marine Heritage of the 6-71 Natural

The Detroit Diesel 6-71 Natural is one of the most iconic inline marine engines ever built. First introduced in the 1930s, the 6-71 powered fishing boats, tugboats, and harbor craft for decades. Its 426 cubic inch displacement, inline-six configuration, and natural aspiration make it rugged, reliable, and straightforward to maintain—key reasons why many vessels still run on this engine today.

Marine Applications

• Fishing Vessels: Long hours at low to mid RPMs demand consistent cooling and fuel efficiency.

• Tugboats & Pushboats: Trusted for torque and reliability in near-shore operations.

• Auxiliary Marine Power: Commonly found in onboard generators and support systems.

Benefits of a 6-71 Natural Marine Long Block

• Saltwater Durability: Built to endure the demanding conditions of marine environments.

• Quick Turnaround: Installing a long block minimizes downtime compared to piecemeal repairs.

• Performance Restoration: Restores original compression and power output for dependable voyages.

• Proven Reliability: Based on decades of engineering that have made the 6-71 a cornerstone of maritime power.

What’s Included in the Long Block

• Assembled block with crankshaft, pistons, and connecting rods.

• Camshaft and marine-spec cylinder heads.

• Precision-balanced rotating assembly.

• Ready to receive external marine components: raw water pump, marine exhaust manifold, and fuel system.

Long Block and Related Components for Detroit Diesel 671 Non-Turbo - (2 Valve Head Type)

Long Block  and Related Components for Detroit Diesel 671 Non-Turbo - (4 Valve Head Type)

Long Block and Related Components for Detroit Diesel 671 Turbo

Detroit Diesel 8V71 Natural Marine Long Block

Legacy of the 8V71 in Marine Service

The Detroit Diesel 8V71 Natural expanded on the 71 Series legacy by introducing a V8 configuration. With a 568 cubic inch displacement, this naturally aspirated powerhouse became a standard in marine propulsion during the mid-20th century. Its compact design fit well in engine rooms where space was limited, while its straightforward two-stroke design ensured consistent operation in challenging maritime environments.

Marine Applications

• Workboats & Ferries: Providing smooth, predictable power for heavy daily use.

• Fishing Fleets: Long trusted in trawlers and seiners where uptime is critical.

• Military & Government Vessels: Used globally for dependable propulsion in patrol boats and landing craft.

Why Choose a Marine Long Block Replacement?

• Direct Drop-In Solution: A long block allows you to reuse external marine components while replacing the entire engine core.

• Reliable Cold Starts: Restored compression ensures dependable ignition, even in cold harbor mornings.

• Extended Service Life: Properly rebuilt long blocks add decades of usability to classic Detroit Diesel vessels.

• Operational Confidence: Keeps your vessel on schedule and reduces the risk of costly breakdowns offshore.

What’s Included in the 8V71 Natural Long Block

• Preassembled V8 block with crankshaft, rods, and pistons.

• Cylinder heads matched to the natural-aspirated marine combustion profile.

• Balanced rotating assembly designed for smooth marine operation.

Ready for installation of marine blower, raw water pump, exhaust, and fuel system components.

Long Block  and Related Components for Detroit Diesel 8V71 Non-Turbo

Long Block  and Related Components for Detroit Diesel 8V71 Turbo

Why Marine Operators Choose Diesel Pro Power

• Global Reach: Shipping Detroit Diesel long blocks to ports and shipyards in over 180 countries.

• Trusted by 40,000+ Customers: Commercial fleets, shipbuilders, and independent captains alike rely on our expertise.

• Marine-Specific Expertise: Every long block is built for the saltwater environment with the durability marine operators demand.

• Fast Turnaround: We understand downtime costs money—our long blocks are ready to ship quickly.