Flexible couplings for boat propeller shafts. Manufactured by R&D Marine, the flexible coupling fits between the boat propeller shaft coupling and the gearbox output coupling. This flexible coupling consists of a contoured flexible disc moulded in tough yet resilient new type Polyester Elastomer. The contoured coupling disc gives clearance for bolt heads, and allows the coupling to flex freely to take up any temporary misalignment of the engine and propeller shaft, due to flexing of the boat structure or the engine moving on its rubber engine mountings. Forward thrust is taken in compression on the coupling disc between the two shaft half couplings and reverse thrust is taken again in compression on the coupling disc between the two fail safe straps. A safety feature of the R&D 910 series flexible couplings is that in the unlikely event of a coupling disc failure, the steel straps make the coupling fail safe and ensure propeller shaft drive is maintained in both forward and reverse. Gearbox Flange Dimensions - Diameter: 127mm (5.00") - Number of gearbox flange bolts: 4 - Coupling bolt hole nominal diameter: 11.2mm (0.44") - Bolt PCD: 107.9mm (4.25") - Coupling register diameter: 63.5mm (2.5") Flexible Coupling Details - Coupling maximum diameter: 143mm (5.63") - Length: 45mm (1.77") - Bolt diameter: 7/16" UNF - Capacity per 100 rpm: 9.69kW 13HP - Coupling approval: Lloyds Register of Shipping & Bureau Veritas - Typical applications: Volvo Penta gearboxes - Electrical properties: Flexible couplings are as standard non-conducting - Earth bonding strip: 807739