A flexible coupling fits in-between the gearbox output flange and the boat prop shaft. The primary role of a flexible coupling is to reduce noise and vibration. There are a number of coupling types available, the choice of which will depend on many factors, including engine horsepower, gearbox reduction, application, budget, space and the results required. Some models are also able to compensate for small degrees of misalignment.
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How to select your Flexible R & D Coupling
You will need the following details:
Engine horse power and engine speed
Gearbox type and reduction ratio
Gearbox flange details: Diameter of flange, diameter of register, pitch circle diameter of fixing holes, size and quantity of holes. (The pitch circle diameter is the distance between the centre of the hole at 12 o'clock position to the centre of the hole at the 6 o'clock position.)
Example: Ford 150 hp @ 2500 rpm PRM 750 2:1 reduction gearbox 6" flange, 3" register, 4.75" PCD, 6 holes, 0.50" diameter To calculate the power of the coupling required. (HP of engine x reduction of gearbox x 100) divided by revs = HP per 100 RPM (150 x 2 x 100) divided by 2500 = 12 HP per 100 RPM Therefore you would need an 807103 R & D flexible shaft coupling