Twin propeller marine propulsion unit

A marine propulsion unit, comprising a housing, a vertical drive shaft journaled in said housing and operably connected to an engine, an inner generally horizontal propeller shaft journaled for rotation relative to said housing, a first propeller connected to said inner propeller shaft, an outer generally horizontal propeller shaft journaled for rotation relative to said housing and disposed concentrically outward of said inner propeller shaft, a second propeller connected to said outer propeller shaft and disposed axially forward of said first propeller, a first bevel gear operably connected to said drive shaft, first clutch means for selectively connecting said first bevel gear to said inner propeller shaft to thereby drive said inner propeller shaft and said first propeller in accordance with rotation of said first bevel gear, a second bevel gear operably connected to said drive shaft and mounted coaxially with said first bevel gear, second clutch means for selectively engaging said second bevel gear with said outer propeller shaft to thereby drive said outer propeller shaft and said second propeller in accordance with rotation of said second bevel gear, said second clutch means being operable separately from said first clutch means, and means responsive to a first elevated engine speed substantially higher than idle speed for operating said second clutch means to thereby operably connect said second bevel gear with said second propeller shaft.

A marine propulsion unit, comprising a housing, a vertical drive shaft journaled in said housing, a beveled pinion gear carried by the drive shaft, a first annular bevel gear operably engaged with said pinion gear, a second bevel gear axially aligned with said first bevel gear and operably connected to said pinion gear, an inner propeller shaft disposed axially within said annular bevel gears and journaled for rotation relative to said housing, a first propeller secured to an end of said inner propeller shaft, an outer propeller shaft disposed concentrically outward of said first propeller shaft and journaled relative thereto, a second propeller connected to said outer propeller shaft and located axially forward of said first propeller, said first bevel gear including a plurality of axially facing teeth, a clutch slidably mounted relative to said inner propeller shaft and rotatably fixed to said inner propeller shaft, said clutch having a neutral position and an engaged position and having a plurality of clutch teeth, means for moving said clutch axially between said neutral and engaged position, said clutch teeth being engaged with the axially facing teeth of said bevel gear when the clutch is in the engaged position to thereby cause rotation of the inner propeller shaft and said first propeller, an annular clutch housing operably connected to said second bevel gear and rotatable therewith, said clutch housing being disposed concentrically outward of said outer propeller shaft, a second clutch disposed within said clutch housing and including a plurality of first clutch discs and a plurality of second clutch discs interdigitated with said first discs, said first clutch discs being slidable longitudinally relative to said clutch housing and being rotatable therewith, said second clutch disc being slidable longitudinally relative to said outer propeller shaft and being rotatable therewith, pressure means disposed within said clutch housing and having a first surface disposed to engage said clutch discs and having an opposite second surface, and hydraulic means for directing a pressurized hydraulic fluid against said second surface to move said clutch discs into driving engagement to thereby drive said outer propeller shaft and said second propeller in the opposite direction from said first propeller.

A watercraft construction, comprising a watercraft to move on a body of water, a marine propulsion unit mounted on the watercraft and including an engine and having a lower housing, said lower housing including a generally torpedo-shaped lower section, a pair of concentric propeller shafts each mounted for rotation relative to said lower section, a first of said propeller shafts disposed radially outward of a second of said propeller shafts, a propeller carried by each propeller shaft with said propellers being located axially of each other, said propeller shafts being operably connected to said engine in a manner to rotate the propeller shafts and the respective propellers in opposite directions to drive the watercraft in a forward direction, an annular bearing carrier disposed in a rear portion of said lower section and located radially outward of said first propeller shaft, bearing means supported by the carrier for journaling the first propeller shaft for rotation, said carrier being provided with a tapered outer surface spaced radially inward from said lower section to provide a space therebetween, a ring disposed in said space and having a tapered inner surface to engage the tapered outer surface of said carrier, and means for threadedly connecting said ring to said lower section whereby threading of said ring in said lower section will urge said first bearing means into engagement with said first propeller shaft.

A marine propulsion unit, comprising a housing, a vertical drive shaft journaled in said housing, a beveled pinion gear carried by said drive shaft, a first annular bevel gear operably connected with said pinion gear, a second bevel gear axially aligned with said first bevel gear and operably connected to said pinion gear, an inner propeller shaft disposed axially within said annular bevel gears and journaled for rotation relative to said housing, a first propeller secured to an end of said inner propeller shaft, an outer propeller shaft disposed concentrically outward of said first propeller shaft and journaled relative thereto, a second propeller connected to said outer propeller shaft and located axially forward of said first propeller, said first and second bevel gears each including a plurality of axially facing teeth, a first clutch slidably mounted relative to said inner propeller shaft and rotatably fixed to said inner propeller shaft, each end of said first clutch having a plurality of axial clutch teeth, means for moving said first clutch axially between a forward position where the clutch teeth on one end of the clutch are engaged with the axial teeth on said first bevel gear and a reverse position where the clutch teeth on the opposite end of said clutch are engaged with the axial teeth on the second bevel gear and a neutral position, said clutch when in the forward position effecting rotation of the inner propeller shaft and said first propeller, an annular clutch housing operably connected to said second bevel gear and rotatable therewith, said clutch housing being disposed concentrically outward of said outer propeller shaft, a hydraulically operated second clutch disposed in said clutch housing, pressure means located in said clutch housing and operably connected to said second clutch for moving said second clutch from a disengaged position to an engaged position, hydraulic means for directing pressurized hydraulic fluid to the pressure means to move said second clutch to the engaged position and thereby drive said outer propeller shaft and said second propeller in the opposite direction from said first propeller, said hydraulic means including pumping means to pressurize said hydraulic fluid, said pumping means being constructed and arranged to deliver pressurized fluid to said pressure member when said first clutch is in said forward position and to prevent delivery of pressurized fluid to said second clutch when said first clutch is in said reverse position.