Abstract: A planetary speed change gearing for a power transmission system including a flywheel secured to a power transmission shaft of an engine, a flywheel housing enclosing the flywheel and an output shaft provided on the flywheel side and directly connected to a machine to be driven. The planetary speed gearing is built in a recess formed in the flywheel.

Abstract: A reduction and reversing gear for marine propulsion systems making use of the clutch case of a conventional reduction and reversing gear of a type having an input shaft mounted on an upper part of the clutch case, an output shaft extending in parallel with the input shaft and mounted on a lower part of the clutch case, a multiple disc clutch carried by the input shaft, a small gear rotatably carried by the input shaft and adapted to be connected to and disconnected from the latter by the multiple disc clutch, and a large gear carried by the output shaft and engaging the small gear. A planetary gear type reduction gear is disposed in the space around the output shaft and below the multiple disc clutch to make an efficient use of that space, thereby to provide an additional reduction stage between the large gear and the output shaft.