Reduction gearbox

A marine reduction gearbox steps the medium- or high-speed engine output down to the lower, more efficient propeller rpm, and can combine several engine inputs onto one shaft, carry a power take-off generator, and house the clutch and shaft brake. Single-reduction ratios run a few to one; twin-input father-and-son arrangements give part-load economy. Tooth and bearing losses are typically 1 to 2 percent per gear mesh.