Abstract: A marine propulsion system with counter-rotating propellers is provided with the capability of causing the propellers to rotate at different speeds. A first gear is attached to an inner propeller shaft and a second gear is attached to an outer propeller shaft. The inner and outer propeller shafts are arranged in coaxial and concentric relation for rotation about an axis of rotation. A driveshaft is connected to a pinion gear which engages the teeth of the fore and aft gears at different effective diameters. The pinion gear meshes with a first plurality of gear teeth on a beveled surface of the fore gear while a second set of gear teeth of the pinion gear mesh with a second plurality of gear teeth on a beveled surface of the aft gear. Because of the different effective diameters of the first and second pluralities of gear teeth, the inner and outer shafts rotate at different speeds.

Abstract: A system for a trimable marine stem drive shifts the trimable range on a conventional hydraulic trim system. The system includes an enlarged cylinder anchor pin hole in the drive shaft housing, an anchor pin smaller in size than the enlarged anchor pin hole located in the drive shaft housing, and a movable trim adjustment insert that is inserted into the enlarged anchor pin hole to secure the anchor pin in a fixed position within the enlarged hole. It is preferred that the enlarged anchor pin hole be a substantially horizontal elongated hole, and that the trim adjustment insert be placed rearward of the anchor pin to position the anchor pin in a forward position, or forward of the anchor pin to locate the anchor pin in a rearward position. The invention shifts the trimable range of the drive, while maintaining vibration isolation characteristics available in conventional hydraulic trim systems.

Abstract: A device is provided for isolating a shift shaft extending through an exhaust passage of a bell housing in a marine drive system. The device includes an elongated sleeve for receiving the shift shaft therein. The sleeve has a first portion sealably mounted in a first bore extending through the top wall of the exhaust passage and a second portion sealably mounted in a second bore which extends through the bottom wall of the exhaust passage. The elongated sleeve prevents galvanic corrosion and erosion of the aluminum housing and the stainless steel shaft.

Abstract: A marine drive (10, 310) has two counter-rotating propellers (12 and 14, 312 and 314). Inner and outer concentric counter-rotating propeller shafts (40 and 42, 340 and 338) are supported by a spool (38, 336) in the lower horizontal bore (28, 328). Passages are provided in the housing for communicating lubrication and/or exhaust with the horizontal bore. Locking structure (50, 404) holds the driven gears and bearings in place in the lower horizontal bore.

Abstract: A marine drive (10) has two counter-rotating surface operating propellers (12 and 14). The drive has a vertical X-dimension (254) in the range of about 13 inches to 19 inches in combination with a shaft-spacing dimension (258) in the range of about 8 inches to 15 inches in combination with a surfacing dimension .gtoreq. zero. In one embodiment, the shaft-spacing dimension is 13.5 inches, the vertical X-dimension is 16 inches, and the surfacing dimension is 2 inches.

Abstract: A surfacing marine drive has a drive housing (20) with a fore exhaust passage (230) forward of the vertical bore (26) housing the driveshaft (36), right and left exhaust passages (232 and 234) extending rearwardly from the fore exhaust passage (230) on opposite right and left sides of the vertical bore (26), and an aft exhaust passage (236) extending rearwardly from the right and left exhaust passages (232 and 234) and aft of the vertical bore (26) and discharging exhaust into dual counterrotating surface operating propellers (12 and 14).

Abstract: A marine drive (10, 310) has two counter-rotating propellers (12 and 14, 312 and 314). Inner and outer concentric counter-rotating propeller shafts (40 and 42, 340 and 338) are supported by a spool (38, 336) in the lower horizontal bore (28, 328). Passages are provided in the housing for communicating lubrication and/or exhaust with the horizontal bore. Locking structure (50, 404) holds the driven gears and bearings in place in the lower horizontal bore.

Abstract: A marine stern drive has an engine output coupler driven to rotate about an axis with a hub that has an axial opening. The forward end of the axial opening is splined and the rearward end is non-splined. The axial opening receives an output driveshaft. The forward end of the driveshaft is splined and engages the splined section of the axial opening so that the engine coupler can rotatably drive the driveshaft. An O-ring seal is provided between the driveshaft and the axial opening in the non-splined section of the axial opening towards the rearward end of the axial opening. An end plug is provided in the forward end of the axial opening for plugging the forward end of the axial opening. A grease passage is provided through the engine coupler to allow grease to be introduced between the seal and the end plug and lubricate the splines. The space between the end plug and the drive plug acts as a grease reservoir. A hole is provided through the end plug to relieve grease pressure and reduce hydraulic lock.

Abstract: A marine drive is provided with a large volume anode, about 30 cubic inches, for galvanic protection. The anode (230) is a brick-like block member tapered along each of its height, width and length dimensions. The drive housing has an anode-mounting section (232) extending rearwardly therefrom and has a downwardly opening cavity (234) of substantially the same shape and volume as the anode, and receiving the anode in nested flush relation.

Abstract: A marine drive (10) has two counter-rotating surface operating propellers (12, 14). Inner and outer concentric counter-rotating propeller shafts (40, 42) are supported by a spool assembly (38) locked and retained against rotation and against axial movement in the lower horizontal bore (28) in the torpedo (34) of the drive housing (26) by axially spaced left and right hand threads (44 and 46). A thrust bearing assembly (98) transfers thrust from the outer propeller shaft to the inner propeller shaft during rotation of the propeller shafts in opposite axial direction and is axially located between fore and aft driven gears (76 and 78). Propeller shaft sealing and bearing structure, and propeller self-centering mounting structure is provided.

Abstract: A marine drive (10) has two counter-rotating surface operating propellers (12 and 14). An upper adaptor spool (48) has a lower threaded outer portion (50) mating with a threaded portion (46) of the vertical bore (26) of the drive housing (20) and supporting the upper gear (42) for rotation about the driveshaft (36) and supporting the driveshaft (36) for rotation within the adaptor spool (48). Vertical bore structure enables assembly from above of the majority of the vertical drive train components into a one-piece unitary integrally cast housing. The vertical distance between the adaptor spool (48) and the lower bearing (118) supporting the vertical driveshaft (36) is about equal to propeller radius. The lower concentric counter-rotating propeller shafts (156, 158) are spaced from the upper input shaft (28) by a distance along the driveshaft (36) in the range of about 9 to 15 inches.

Abstract: A marine drive (10) has a driveshaft housing (20) including a bell housing (22) with an exhaust passage (30) therethrough directing exhaust gas and cooling water, and a shift shaft (34) extending through the exhaust passage and journaled in the bell housing by a bushing (52) in a bore (38) in a section (40) of the bell housing. The interface (50) of the bushing and the bore is subject to corrosion from exhaust gas and cooling water. Shifting is eased by enabling a portion (54) of the bushing to contract radially inwardly toward the shift shaft (34) due to the noted corrosion, without binding the shift shaft and otherwise impeding rotation thereof.

Abstract: A marine stern drive (10) has an engine output coupler (60) driven to rotate about an axis and having a hub (70) with a splined axial opening (72) therein which is open-ended at the front and rear. A splined output driveshaft (78) is received in the splined axial opening (72) of the coupler hub (70) and is operatively coupled to the boat propeller (20) to drive same. The coupler hub (70) has a grease fitting (74) therein and a grease passage (76) extending from the grease fitting (74) and communicating with the splines (80, 82) to lubricate same. Front and rear sealing O-rings (84, 86) trap and retain the grease therebetween to maintain lubrication of the splines. The axial opening in the hub has a forward splined section (88) and a rearward nonsplined section (90). The driveshaft has a forward nonsplined section (90), a splined section (94) axially rearward of the forward section (92), and another nonsplined section (96) axially rearward of the splined section (94).