Abstract: An oil seal for sealing a hollow rotary shaft in a power transmission apparatus, wherein the rotary shaft is formed with an internal flow passage through which oil flows and constituted such that the oil flies out as the rotary shaft rotates, including: a fixed portion that is fixedly attached to a case of the power transmission apparatus; a seal portion that seals the rotary shaft at a position that is axially offset position from the fixed portion and allows the rotary shaft to rotate; and a radiator portion that is formed from a metallic material between the fixed portion and the seal portion, receives the oil that flies out as the rotary shaft rotates, and dissipates heat generated by the seal portion by exchanging heat with the oil.

Abstract: An oil seal for sealing a hollow rotary shaft in a power transmission apparatus, wherein the rotary shaft is formed with an internal flow passage through which oil flows and constituted such that the oil flies out as the rotary shaft rotates, including: a fixed portion that is fixedly attached to a case of the power transmission apparatus; a seal portion that seals the rotary shaft at a position that is axially offset position from the fixed portion and allows the rotary shaft to rotate; and a radiator portion that is formed from a metallic material between the fixed portion and the seal portion, receives the oil that flies out as the rotary shaft rotates, and dissipates heat generated by the seal portion by exchanging heat with the oil.

Abstract: A drive of inboard-and-outboard engines, wherein a drive gear unit (10) meshing with driven gears (25, 26) disposed on the upper end side of a drive shaft (28) disposed generally in vertical direction is formed slidably in a direction perpendicular to the drive shaft (28), whereby the drive gear unit (10) can be operated slidably from the outside of an upper unit (9) located at the top of an outer drive unit (5) disposed inside a hull (1).