CA2468315C - Marine propulsion machine - Google Patents

Abstract

An outboard motor includes a forward/backward selector provided with a selector mechanism including a clutch mechanism for selecting a forward-drive mode or a backward--drive mode, and a selector-operating rod for operating the clutch mechanism. The selector-operating rod is formed by connecting an upper rod and a lower rod. The lower rod has an upper portion capable of being detachably connected to the upper rod, and a middle portion having an upper end joined to the upper portion. The lower rod is inserted slidably in a gear case in a liquid-tight fashion such that the middle portion is entirely contained in a sealed space formed in the case, and a connecting end of the upper portion extends outside the case. The upper portion exposed to water and the middle portion not exposed to water are formed of different materials, so that the cost of the outboard engine can be reduced.

Description

SPECIFICATION
MARINE PROPULSION MACHINE
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to a marine propulsion machine, such as an outboard motor or engine, and, more specifically, to a selector-operating rod for controlling a selector mechanism included in a forward/backward selector.
Description of the Related Art An outboard motor or engine disclosed in, for example, JP 57-140294 A has a selector-operating rod to be operated to select a propeller rotational direction includes a first rod and a second rod axially separably connected to the first rod.
The first and the second rod are coupled together by a connector fastened to a lower end part of the first rod or to an upper end part of the second rod. The connector is inserted in a bore formed in an upper casing such that an upper end part of the connector and the first rod extend outside the bore, and a lower end part of the connector and an upper end part of the second rod extend in a space defined by the upper casing and a lower casing. A dog clutch that is operated by the se-lector-operating rod to change the rotational direction of the propeller, and a gear mechanism including a forward gear and a backward gear, which are selectively engaged with the dog clutch, are contained in the lower casing.
In this prior art outboard motor or engine, water, such as seawater, leaks through the bore into the space containing the lower end part of the connector and the upper end part of the second rod, and wets the second rod. Therefore, the first and the second rod forming the selector-operating rod must be formed of a material excellent in corrosion resistance, and such a corrosion-resistant material increases the cost of the selector-operating rod.
The present invention has been made in view of such a problem and it is therefore a principal obj ect of the present invention to provide a marine propulsion machine provided with a selector-operating rod that can be manufactured at a low manufacturing cost and hashigh corrosion resistance. Another object of the present invention is to provide a lightweight marine propulsion machine having a good external appearance.
SUMMARY OF THE INVENTION
The present invention provides , to achieve the obj ect, a marine propulsion machine including: a forward/backward selector provided with a selector mechanism for selecting one of a forward-drive mode or a backward-drive mode; a case containing the selector mechanism; and a selector-operating rod for operating the selector mechanism, having a first rod disposed on an operating side and a second rod detachably connected to the first rod; wherein the second rod has an input portion detachably connected to the first rod, and a middle portion formed of a material different from that of the input portion and fixedly joined to the input portion, the case has a watertight sealed space therein, and the second rod is inserted slidably in the case in a liquid-tight fashion such that the middle portion is entirely contained in the sealed space and the input portion extends outside the case.
The input portion of the second rod of the built-up selector-operating rod extends outside the case. Therefore the input portion can be exposed to water and can be immersed in or wetted with water while the ship is cruising or at anchor,.
and can be exposed to air and kept in an corrosive atmosphere during tilt-up. Therefore, the input portion must be formed of a highly corrosion-resistant material. On the other hand, the middle portion of the second rod fixedly joined to the input portion is contained entirely in the sealed space and is not exposed to water. Therefore, the middle portion does not need to be formed of a corrosion-resistant material. Thus, the middle portion may be formed of an inexpensive material to reduce the cost of the marine propulsion machine.
According to the present invention, the input portion and the first rod extending outside the case may be formed of the same material.

Since the input portion and the first rod, which are exposed and extend outside the case, are formed of the same material, the external appearance of the selector-operating rod is not spoiled even if the input portion and the middle portion of the second rod are formed of different materials, and hence the marine propulsion machine can be formed in a good external appearance.
Preferably, the input portion and the first rod are formed of a corros ion-resistant material , and the sealed space is filled up with a lubricating oil and mists of the lubricating oil.
According to the present invention, the middle portion of the second rod may be a pipe. The hollow middle portion is light as compared with a corresponding solid member, which is advantageous to the weight reduction of the marine propulsion machine.
Typically, the sealed space is a space for containing the selector-operating rod, having an open upper end opening in the upper end surface of the case and extending downward from the upper end surface of the case, a holder provided with a sealing member for covering the open upper end is fitted in the open upper end, and the input portion of the second rod penetrates the holder in a liquid-tight fashion. The holder provided with the sealing member seals the sealed space to prevent the leakage of water into the sealed space.
Typically, a lower part of the sealed space connects with a gear chamber containing the forward/backward selector, a bearing structure is formed in the lower part of the sealed space, the second rod has an output portion j oined to one end of the middle portion opposite the other end of the same to which the input portion is j oined, and the output portion is supported in the bearing structure.
Desirably, the middle portion is longer than the input and the output portion. The cost of the selector-operating rod can be reduced by forming the middle portion of an inexpensive material in a length such that the ratio of the length of the middle portion to that of the selector-operating rod is large.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic right side elevation of an outboard motor or engine in a_ preferred embodiment of the present invention;
Fig. 2 is a sectional view of an essential part of the outboard engine shown in Fig. 1 taken in a plane including the axis of a swivel shaft included in the outboard engine;
Fig. 3 is a sectional view, similar to Fig. 2, of a gear case and associated parts included in the outboard engine shown in Fig. l;
Fig. 4A is a front elevation of a selector-operating rod included in the outboard engine shown in Fig. 1; and Fig. 4B is a side elevation taken on the line B-B in Fig.

4A.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment of the present invention will be described with reference to Figs. 1 to 4.
An outboard motor or engine 1 will be described with reference to Fig. 1. The terms "right side" and "left side"
correspond to the starboard and the port, respectively, of the hull of a ship on which the outboard engine 1 is mounted. The outboard engine 1 includes a main engine unit 2 having an internal combustion engine E and a propulsion unit P provided with a propeller 17 driven by the internal combustion engine E to generate driving force, and a supporting device 3 for supporting the main engine unit 2 on a hull B.
The internal combustion engine E is a water-cooled, four-in-line, four-stroke cycle, overhead-camshaft internal combustion engine. The internal combustion engine 1 has an engine unit 4 including a cylinder block 4a and a crankcase 4b joined to the front end of the cylinder block 4a. A vertical crankshaft 5 having a vertical axis is supported for rotation between the cylinder block 4a and the crankcase 4b.
In the following description, the terms "vertical", "longitudinal" and"transverse" are used to express directions and positions with reference to the hull B on which the outboard engine 1 is mounted, and it is assumed that the outboard engine 1 is disposed with a swivel axis L about which the main engine unit 2 swivels in a horizontal plane extended vertically. An upper and a lower end part of a member correspond to one and the other end part of the member, respectively.
The engine unit 4 is mounted on a mount case 6. An oil case 7 having an oil pan and a side wall is j oined to a lower part of the mount case 6. A tubular lower cover 8 covers a lower part of the engine unit 4 , the mount case 6 and oil case 7. The lower cover 8 is joined to the oil case 7 or an extension case 10. An upper cover 9 covering an upper part of the engine unit 4 is joined to the upper end of the lower cover 8. The upper cover 8 and the lower cover $ engaged with a flange formed on the mount case 6 define an engine compartment for containing the engine unit 4 over the mount case 6. The extension case is joined to the lower end of the oil case 7, and a gear case 11 is joined to the lower end of the extension case 10.
The bottom wall of the mount case 6, the side wall of the oil case 7 and the extension case 10 defines an exhaust chamber.
The exhaust chamber is connected to an exhaust passage formed in the gear case 11.
An upper end part 12a of a drive shaft 12 is connected to a lower end part 5b of the crankshaft 5. The drive shaft 12 extends vertically coaxially with the crankshaft 5. The drive shaft 12 extends vertically downward from the lower end part 5b of the crankshaft 5 through the mount case 6 and the extension case 10 into the gear case 11. The drive shaft 12 is operatively connected to a propeller shaft 16 by a for-ward/backward selector 13 including a gear mechanism 14 and a clutch mechanism 15 and contained in the gear case 11. The power of the internal combustion engine E is transmitted from the crankshaft 5 through the drive shaft 12 , the forward/backward selector 13 and the propeller shaft 16 to a propeller 17 to rotate the propeller 17. The drive shaft 12 and the for-ward/backwardselectorl3constitute a power transmission. The power transmission, the propeller shaft 6, the propeller 17, the lower cover 8, the extension case 10 and the gear case 11 constitutes the propulsion unit P. The internal combustion engine E, the propulsion unit P and the upper cover 9 constitute the main unit of the outboard engine 1.
Referring to Fig. 2 as well, the supporting device 3 has a pair of stern brackets 20 detachably attached to the hull B, a swivel case 22 supported for tilting in a vertical plane on a tilt shaft 21 attached to the stern brackets 20, and a mount frame 23 supporting the main engine unit 2 and supported for turning in a horizontal plane on a bearing part 22a of the swivel case 22.
The mount frame 23 has a swivel shaft 23a rotatably fitted in the bore of the bearing part 22a, a pair of upper mounting parts 23b extending from an upper part of the swivel shaft 23a, a lower mounting part 23b detachably attached to a lower end part of the swivel shaft 23a, and a control arm 23d extending forward from an upper end part of the swivel shaft 23a.
The main engine unit 2 is supported on the mount frame 23 . In an upper part of the main engine unit 2 , the mount case 6 is fastened to the upper mounting parts 23b with bolts with an upper rubber mount 24 held between the mount case 6 and the upper mounting parts 23b. In a lower part of the main engine unit, the extension case 10 is fastened to the lower mounting part 23c with bolts with a pair of lower rubber mounts 25 held between the extension case 10 and the lower mounting part 23c.
A steering handle, not shown, connected to the control arm 23d is operated to turn the main engine unit 2 in a horizontal plane about the center axis L of the swivel shaft 23a for steering.
The outboard engine 1 is intended for use as a power unit for small hydroplanes , such as motorboats and fishing boats .
Therefore, the outboard engine 1 is mounted on the stern of the boat with an anticavitation plate lla being level with the bottom of the boat in order that the outboard engine 1 is able to exert the heighst driving force while the boat is planing on the surface of the water. When the boat is at anchor or cruising at a low speed, the draft of the boat increases, and a part of the outboard engine 1 below the lower mounting part 23c is immersed in water . When the draft increases to a maximum, a part below a part around the upper mounting parts 23b near the upper end of the stern is immersed in water.

Referring to Figs . 1 and 3 , the forward/backward selector 13 is held in a gear chamber 30 formed in the gear case 11.
The drive shaft 12 is supported for rotation in bearings 31 and 32 in the gear case 11. A propeller shaft holder 33 is joined to the gear case 11. The propeller shaft holder 33 supports a propeller shaft 16 perpendicular to the drive shaft 12 for rotation. A sealing member 27 is held by a holder 26 fixed to the gear case I1 in a liquid-tight fashion. The drive shaft 12 is extended through the sealing member 27 in a liquid-tight fashion.
The gear chamber 30 is a sealed space filled up with a lubricating oil and mists of the lubricating oil. The gear mechanism 14 is held in the gear chamber 30 . The gear mechanism 14 is a bevel gear mechanism having a drive gear 34 fixedly mounted on a lower end part 12b of the drive shaft 12, a forward gear 35 rotatably mounted on a front part 16a of the propeller shaft 16, and a backward gear 36 rotatably mounted on the front part 16a of the propeller shaft 16 opposite to the forward gear 35 with respect to the drive gear 34. The drive gear 34 is always engaged with the forward gear 35 and the backward gear 36.
The clutch mechanism 15 is mounted on the front part 16a of the propeller shaft 16. The cutch mechanism 15 has a shifter 37 slidably fitted in a bottomed central bore 16b formed in the front part 16a coaxial with the propeller shaft 16, a cylindrical clutch element 38 put on the front part 16a, and a shift pin 39 interlocking the shifter 37 and the clutch element 38.
The shifter 37 is moved axially in axial directions A
indicated by the arrows parallel to the center axis of the propeller shaft 16 by operating a selector-operating rod 40.
The shifter 37 includes a cylindrical first shifting member 37a provided with an interlocking part 37d engaged with the selector-operating rod 40, and a cylindrical second shifting member 37b. The second shiftingmember 37bhas one end connected to the first shifting member 37a with a connecting pin 37c.
The shift pin 39 penetrates the second shifting member 37b diametrically.
A front end part of the first shifting member 37a is supported axially slidably in a bearing part 18 formed in the gear case 11. The interlocking part 37d has a pair of flanges 37d1 and 37d2 formed integrally with the first shifting member 37a. An operating member6lincludedin theselector-operating rod 40 is disposed between the flanges 37d1 and 37d2. The operatingmember 61 is engaged selectively with either the flange 37d1 or the flange 37d2 to move the shifter 37 in the axial direction A when the selector-operating rod 40 is turned. The second shifting member 37b is a hollow member having opposite open ends.
A positioning mechanism for positioning the shifter 37 at a neutral position is disposed between the first shifting member 37a and the shift pin 39. In this embodiment, the positioning mechanism is a detaining mechanism 37e including a pair of coil springs, a pair of pressing steel balls pushed by the coil springs, respectively, and a pair of positioning steel balls pressed radially outwardby the pressing steel balls , respectively. The shift pin 39 is extended through a pair of axial slots 16a1 formed parallel to the axial directions A in the front part 16a. Opposite ends of the shift pin 39 are connected to the clutch element 38.
The clutch element 38 is mounted on and interlocked with the front part 16a by splines so as to be slidable in the axial directions A. The clutch element 38 is an axially slidable member of a dog clutch. The clutch element 38 has one end surface provided with forward teeth and the other end surface provided with reverse teeth. The forward teeth of the clutch element 38 are engaged with teeth formed on the forward gear 35 when the forward-drive mode is selected, and the backward teeth of the clutch element 38 are engaged with teeth formed on the backward gear 36 when the backward-drive mode is selected.
When the selector-operating rod 40 is operated to position the shifter 37 at the neutral position, the clutch element 38 is disengaged from both the forward gear 35 and the backward gear 36. Although the forward gear 35 and the backward gear 36 are driven by the drive gear 34 in this state, the rotation of the drive shaft 12 is not transmitted to the propeller shaft 16. When the shifter 37 is positioned at a forward-drive position, the forward teeth of the clutch element 38 are engaged with the teeth of the forward gear 35. Consequently, the rotation of the drive shaft 12 is transmitted through the forward gear 35 and the clutch element 38 to the propeller shaft 16 to drive the propeller shaft 16 and the propeller 17 for rotation in the normal direction. Then, the boat is driven ahead. When the shifter 37 is positioned at a backward-drive position, the backward teeth of the clutch element 38 are engages with the teeth of the backward gear 36. Consequently, the rotation of the drive shaft 12 is transmitted through the backward gear 36 and the clutch element 38 to the propeller shaft 16 to drive the propeller shaft 16 and the propeller 17 for rotation in the reverse direction. Then, the boat is driven astern. Thus, the clutch mechanism 15 serves as a forward/backward selecting mechanism for selecting either the forward-drive mode or the backward-drive mode.
Referring to Figs. 1 to 3, the control mechanism for controlling the clutch mechanism 15 has a drive mechanism 19, partly shown in Fig. 2, mounted on the mount case 6, the selector-operating rod 40 having an upper end part 40a interlocked with the drive mechanism 19 by splines to operate the clutch mechanism 15, and a operating mechanism, not shown, to be operated by the user to operate the drive mechanism 19.

The selector-operating rod 40 is disposed in front of the drive shaft and extends vertically substantially parallel to the drive shaft 12. The selector-operating rod 40 extends from outside the propulsion unit P (or the main engine unit 2 into the propulsion unit ) (or the main engine unit 2) . The selector-operating rod 40 extending downward from the drive mechanism 19 extends through the hollow swivel shaft 23a, extends further from the swivel shaft 23a through an opening l0a (Fig.
2) formed in the extension case 10 and through an internal space lOc formed in the extension case 10 into the gear case 11.
The selector-operating rod 40 is a two-part rod having an upper rod 41 , i . a . , a first rod, and a lower rod 42 , i . a . , a second rod.
The upper rod 41 extends downward from a position near the mount case 6 provided with the driving mechanism 19 through the swivel shaft 23a into the extension case 10. The lower rod 42 is disposed in the internal space lOc of the extension case 10. The upper rod 41 and the lower rod 42 are connected reparably by a connecting member 43 forming a lower end part 41b of the upper rod 41. As shown in Fig. 4A, the connecting member 43 is a tubular member welded to a solid lower end part 41c of the upper rod 41 . The connecting member 43 may be formed integrally with the lower end part 41c . The connecting member 43 is provided with internal splines.
The upper rod 41 extends outside the propulsion unit P

(or the main engine unit 2) and through the internal space lOc into which rainwater and seawater leak through the opening 10a, and an opening lOb through which a pipe 28 for transmitting water pressure for cruising speed measurement extends. Thus, the upper rod 41 extends in a wettable space in which the upper rod 41 is exposed to water. In this specification, "wettable space" signifies a space around the propulsion unit P (or the main engine unit 2) and the internal space lOc that are exposed to air when the outboard engine I is tilted up, and are wetted with rainwater and water, such as seawater and splashed water, while the boat is cruising.
Referring to Fig. 4A, the lower rod 42 has an upper portion 50 having a connecting part 51 reparably connected to the upper rod 41, a lower portion 60 provided with a shifter operating member 61 for shifting the shifter 37 to control the clutch mechanism 15, and a middle portion 70 having an upper end 70a fixedly j oined to the upper portion 50 by a welded j oint 81 , and a lower end 70b fixedly joined to the lower portion 60 by a welded joint 82. The upper portion 50, the lower portion 60 and the middle portion 70 are separate members.
The upper member 50 has the connecting part 51 provided with external splines and formed in the upper end 42a of the lower rod 42 , and a spring seat 52 formed below the connecting part 51 . The connecting part 51 of the upper rod 50 proj ects upward from the upper end surface llb of the gear case I1 into the internal space 10c of the extension case 10. The external splines of the connecting part 5I are engages with the internal splines of the connecting member 43 in the internal space lOc.
As shown in Figs . 2 and 3 , the spring seat 52 has an upper end in contact with a holder 44 and a lower end on which a spring 55 is seated to push the lower rod 42 toward a lower end 42b.
In this embodiment, the spring seat 52 is a washer supported on a retaining ring 54 fitted in an annular groove 53 (Fig.
4A) formed in the upper portion 50. The spring seat 52 may be formed integrally with the upper portion 50.
The lower portion 60 has the operating member 61 j oined to the lower end 42b of the lower rod 42, a journal 62 and a flange 63. The journal 62 and the flange 63 are arranged in that order toward the middle portion 70 . The operating member 61, the journal 62 and the flange 63 are formed integrally with the lower portion 60.
As shown in Fig. 4B, the operating member 61 is eccentric with respect to the axis of the journal 62 and is placed between the flanges 37d1 and 37d2 of the shifter 37. When the se-lector-operating rod 40 is turned, the operating member 61 revolves about the axis of the selector-operating rod 40 to move the shifter 37 in the axial directions A to locate the shifter 37 selectively at the neutral position, the for-ward-drive position or the backward-drive position.
The journal 62 is supported rotatably in a bearing part 46 of the gear case 11 to support the lower end 42b of the lower rod 42 rotatably on the gear case 11. The flange 63 is seated on the bearing part 46 serving as a thrust bearing. The spring 55 presses the flange 63 against the bearing part 46 to restrain the axial movement of the lower rod 42 and to prevent the lower rod 42 from shaking.
The lower rod 42 extends downward from the internal space lOc through a sealed bore llc formed in the gear case 11 and connecting with the gear chamber 30 into the gear chamber 30.
The sealed bore llc, similarly to the gear chamber 30, is a sealed space filled up with the lubricating oil and mists of the lubricating oil and sealed so that water is unable to leak in.
More concretely, the upper member 50 of the lower rod 42 is held rotatably by the holder 44 attached to the gear case 11 so as to close the open upper end llcl of the sealed bore llc opening in the upper end surface llb of the gear case 11 in a liquid-tight fashion. The upper portion 50 is supported movably, slidably in this embodiment, and in a liquid-tight fashion in a sealing member 45 attached to the holder 44 . Thus , the upper portion 50 extends through the holder 44 and the gear case 11.
Thus , the upper portion 50 is held in a liquid-tight fashion on the gear case 11 and extends in a liquid-tight fashion through the gear case I1 into the sealed bore 11c. The connecting part 51 in the upper end part of the upper member 50 is contained entirely in the internal space lOc, and the spring seat 52 and the welded joints 81 of the upper member 50 are contained in the sealed bore llc. The sealing member 45 prevents water from leaking in the sealed bore llc filled up with the lubricating oil and mists of the lubricating oil.
The lower portion 60 of the lower rod 42 extends through an opening llcz formed at the lower end of the sealed bore 11c and connecting with the gear chamber 30 . The flange 63 is placed in the sealed bore llc, and the operating member 61 is placed in the gear chamber 30. The opening 11c2 is formed such that the operating member 61 is able to pass through the opening llcz . Thus , the welded j oint 82 and the flange 63 of the lower portion 60 are contained entirely in the sealed bore llc, and the operating member 61 of the lower portion 60 is contained in the gear chamber 30. The middle portion 70 of the lower rod 42 is contained entirely in the sealed bore 11c.
An upper part between a surface in contact with the sealing member 45 and the connecting part 51 of the upper portion 50 lie in the internal space lOc, i.e. , a space extending outside the gear case 11 and permitting water to leak in, and a lower part between the surface in contact with the sealing member 45 and the middle portion 70 lie in the sealed bore llc. Thus, it is possible that the part between the surface in contact with the sealing member 45 and the connecting part 51 of the upper portion 50 of the lower rod 42 is exposed to water, whereas the lower part lying in the sealed bore 11c and the gear chamber 30 are not exposed to water.
Therefore, upper rod 41 extended in the wettable space where the upper rod 41 is subject to rusting due to exposure to air and water, i . a . , a corrosive environment where the upper rod 41 is wetted with or immersed in seawater containing salt, is formed of a highly corrosion-resistant material, such as a stainless steel.
On the other hand, the part, including the connecting part 51 and extended in the internal space lOc in the extension case, of the upper portion 50 of the lower rod 42, i.e., the part, extending outside the gear case 11, of the upper portion 50 of the lower rod 42 , similarly to the upper rod 41 , is extended in the wettable space in which water leaks while the boat is cruising, and is exposed to water and air . The upper portion 50 of the lower rod 42, similarly to the upper rod 41, is formed of a highly corrosion-resistant material, such as a cor-rosion-resistant metal, a stainless steel in this embodiment.
Since the lower portion 60 has the operating member 61 engaged with the interlocking part 37d, and sl iding parts , i . a . , the journal 62 and the flange 63, the lower portion 60 is formed of a highly abrasion-resistant material, such as a carburizing steel.
The corrosion-resistant parts may be formed of a highly corrosion-resistant material or may be corrosion-resistant parts treated by a surface treatment for increasing the corrosion resistance of their surfaces. Similarly, the abra-sion-resistant parts may be formed of a highly abra-sion-resistant material or may be abrasion-resistant parts treated by a surface treatment for increasing the abrasion resistance of their surfaces.
The middle portion 70 , which is a straight pipe having the same inside diameter and the same outside diameter, is formed of a material inferior in corrosion resistance to and less expensive than the materials forming the upper rod 41 and the upper portion 50 of the lower rod 42, such as a stainless steel.
The middle portion 70, for example, is a steel pipe formed of a carbon steel . A pipe as cut in the length of the middle portion 70 is used as the middle portion 70 of the lower rod 42.
The upper portion 50 and the lower portion 60 are formed in the shortest possible length permitting the formation of the spring seat 52 , the j ournal 62 and the flange 63 therein .
The middle portion 70 is formed in a length longer than those of the upper portion 50 and the lower portion 60.
The operation and effect of the embodiment will be explained.
In the outboard engine 1, the lower rod 42 reparably connected to the upper rod 41 to form the selector-operating rod 40 for operating the clutch mechanism 15 of the for-ward/backward selector 13 has the upper portion 50 and the middle portion 70 formed of a material different from that forming the upper portion 50 . The middle portion 70 is extended entirely in the liquid-tight sealed bore 11c, and the upper portion 50 of the lower rod 42 is extended slidably through the sealing member 45 in a liquid-tight fashion into the gear case 11 with the connecting part 51 of the upper portion 50 proj ecting outside the gear case 11 into the internal space lOc of the extension case 10. Thus, the upper portion 50 lies in an environment where the upper portion 50 is immersed in water while the boat is cruising at low speed and at anchor, wetted with rainwater, splashed with water while the boat is cruising, and exposed to air and undergoes corrosion while the outboard engine 1 is tilted up. Therefore, the upper portion 50 of the lower rod 42 is formed of a highly corrosion-resistant material. Since the middle portion 70 fixedly joined to the upper portion 50 is contained entirely in the sealed bore 11c and is not exposed to water, the middle portion 70 does not need to be formed of a highly corrosion-resistant material and may be formed of a material less corrosion-resistant and less expensive than the material of the upper portion 50. Thus, the middle portion 70 can be formed of an inexpensive material to reduce the cost of the outboard engine 1.
The lower rod 42 has the upper portion 50, the middle portion 70 and the lower portion 60, namely, three separate portions or members . The upper portion 50 having the connecting part 51 and the spring seat 52 is fixedly joined to the upper end 70a of the middle portion 70. The lower portion 60 having the operating member 61, the j ournal 62 and the flange 63 is fixedly joined to the lower end 70b of the middle portion 70.
Since the middle portion 70 needs only to transmit an operating force exerted on the selector-operating rod 40 , the upper portion 50 and the lower portion 60 can be used as members common to different types of outboard engines by forming lower rods 42 having the members of different lengths. Consequently, the cost can be reduced. Since the upper portion 50, the middle portion 70 and the lower portion 60 can be formed of optimum materials meeting the requisite functions thereof, re-spectively, the excellent selector-operating rod 40 can effectively exercise the corrosion resistance of the upper portion 50 , the force transmitting function of the middle portion 70 and the abrasion resistance of the lower portion 60.
Since the middle portion 70 is a pipe of a desired length substantially as it is cut obtained simply by cutting a pipe by a cutting process, the cost of the outboard engine 1 can be reduced.
Since the upper portion 50 of the lower rod 42 and the upper rod 41 extending in the internal space 10c extending outside the gear case 11 are formed of the same material, the external appearance of the selector-operating rod 40 is not spoiled by forming the upper portion 50 and the middle portion 70 of the lower rod 42 are formed of different materials, respectively. Thus, the selector-operating rod 40 has a satisfactory external appearance and hence the outboard engine 1 has a satisfactory external appearance.
Since the middle portion 70 is a pipe having a bore, the selector-operating rod 40 can be formed in a light weight and hence the weight of the outboard engine 1 can be reduced.
In a modification, the selector-operating rod 40 may be a multiple part rod consisting of three or more members instead of the two-part rod. When the selector-operating rod 40 is a multiple-part rod consisting of three or more component rods, the two rods, i.e., a first rod and a second rod separably connected to the first rod, are those conforming to the present invention. The marine propulsion machine may be an in-board-outboard engine.
The middle portion 70 may be a slid bar instead of the pipe. The flange 63 may be a separate member fixedly attached to the lower portion 60 by suitable attaching means, such as welding instead of a flange formed integrally with the lower portion 60.
The upper end part 12a of the drive shaft 12 may be j oined to the lower end of an output shaft operatively connected to the crankshaft 5 instead of being connected to the lower end part 5b of the crankshaft 5.

Claims (3)

1. A marine propulsion engine comprising:

a forward/backward selector provided with a selector mechanism for selecting one of a forward-drive mode or a backward-drive mode;

a case containing the selector mechanism; and a selector-operating rod for operating the selector mechanism, having a first rod disposed on an operating side and a second rod detachably connected to the first rod;

wherein the second rod has an input portion detachably connected to the first rod, and output portion having an operating member for operating the selector mechanism, and a middle portion formed of a material different from the material of the input portion and from the material of the output portion, said middle portion being fixedly joined to the input portion through a first joint and to the output portion through a second joint;

wherein the case has a watertight sealed space therein, and the middle portion, the first joint and the second joint are positioned within said watertight sealed space;

wherein said input portion is inserted slidably in the case in a liquid-tight fashion such that a part of the input portion is within said watertight sealed space and another part of the input portion is positioned outside the case; and wherein said input portion is made of a corrosion-resistant material, said middle portion is made of a material less expensive that the material of the input portion, and said output portion is made of an abrasion-resistant material.

2. The marine propulsion engine according to claim 1, wherein said input portion is made of a material which is same as a material which the first rod is made of.

3. The marine propulsion engine according to claim 1, wherein said part of the input portion within the watertight sealed space has a spring seat for seating a spring for urging the second rod downward.