Manufactured by R&D Marine, the flexible coupling fits between the boat propeller shaft coupling and the Twin Disc gearbox output coupling. This flexible coupling consists of a contoured flexible disc molded 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.152.4mm maximum coupling diameter49.8mm Length1/2" UNF bolt diameterFitted with a shouldered bush to locate in the gearbox flange20.88kW, 28HP capacity per 100RPMTypical applications includes twin disc MG gearboxes with 6" coupling flangeEarth bonding strip5.75" Gearbox Output Coupling Diameter6 gearbox flange bolts16mm Coupling bolt hole nominal diameter120.6mm Bolt PCD76.2mm Coupling register diameter