R & D Flexible Shaft Coupling f/4" B/W, Hurth - 5HP/100RPM Capacity

The R & D Flexible Shaft Coupling for 4" B/W, Hurth represents a critical drivetrain component designed to handle the constant stress of marine propulsion systems. Built by R & D Marine, this flexible shaft coupling is engineered to absorb misalignment and vibration that naturally occurs between engine and transmission on vessels of all sizes, protecting both components from premature wear and catastrophic failure.

The coupling features a contoured polyurethane flexible disc molded for resilience and durability in saltwater and freshwater environments alike. This disc design provides bolt head clearance while remaining free to flex and compensate for any temporary misalignment caused by engine movement on vibration isolation mounts or the flexing of the boat structure itself. With a 5HP/100RPM capacity rating, this coupling is sized for smaller to mid-range marine engines commonly paired with Hurth transmission systems. Forward thrust is taken in compression on the disc, allowing the coupling to handle both propulsive and reversing loads that occur during normal boating operations.

This coupling is essential for weekend fishermen running inboard powerboats, recreational cruisers, and working vessels that depend on reliable drivetrain performance. The 4-inch bore fits Hurth transmission flanges and is compatible with standard 4-inch shaft applications. Proper installation requires alignment check and torque specifications; worn or damaged couplings should be replaced to prevent further damage to the transmission or engine mounts. Maintenance includes periodic inspection for disc wear and bolt tightness, particularly in high-use or saltwater applications where corrosion and fatigue accelerate degradation.