JP2002256860A - Exhaust emission control catalyst device for outboard motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control catalyst device for an outboard motor capable of easily and detachably attaching a catalyst and also aligning a plurality of catalysts without complicating the structure of the flow guide for an exhaust gas. SOLUTION: The feeding passage 37 and return passage 38 of an exhaust gas are formed in an exhaust gas flow guide 12 supporting an engine in which a crankshaft is disposed longitudinally, and the catalysts 41 and 42 are arranged in the middle of an exhaust passage 40 communicating with the feeding and return passages 37 and 38. In the exhaust emission control catalyst device composed like this, the exhaust pipe 39 forming the exhaust passage 40 is composed independently of the flow guide 12 and also is detachably attached thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust catalyst device for an outboard motor in which a catalyst is arranged in the middle of an exhaust passage of an engine.

[0002]

2. Description of the Related Art Generally, an outboard motor mounted on a small boat has an upper case and a guide exhaust connected to an upper part of a lower case in which a propulsion device is provided, and an engine is supported on the guide exhaust. The propulsion unit is covered with a cowling and rotates the propulsion unit by an engine to generate a required propulsion force. Exhaust gas from the engine is discharged into the water through a guide exhaust, an upper case, and a lower case through an exhaust passage formed in the cylinder body in a vertical direction.

Meanwhile, in recent years, exhaust gas regulations have been applied to outboard motors, and proposals have been made to provide a catalyst in an exhaust passage for the purpose of purifying exhaust gas. For example,
Japanese Patent Application Laid-Open No. Hei 7-189671 discloses a configuration in which a catalyst is provided in an upper case below an engine, and Japanese Patent Application Laid-Open No. Hei 4-260893 discloses a structure in which a catalyst is provided in an exhaust passage formed in a cylinder body of an engine. The configuration provided is disclosed.

However, in the system in which the catalyst is provided in the upper case below the engine, it is necessary to raise and curve the exhaust passage so that the catalyst does not come into contact with water, so that the exhaust passage is curved in a restricted cowling space. There is a problem that it is not easy.

Further, in a system in which a catalyst is provided in an exhaust passage formed in a cylinder body of an engine, a large volume cannot be secured in the catalyst due to a limitation of a mounting space, and the catalyst is not sufficient for purification of exhaust gas. There is a problem that the effect cannot be obtained.

Therefore, there has been proposed a structure in which an exhaust passage extending in a horizontal direction is formed in a guide exhaust supporting an engine, and a catalyst is horizontally disposed in the middle of the exhaust passage (see Japanese Patent Application Laid-Open No. 9-494424). .

[0007]

However, if the configuration according to the above proposal is adopted, the structure of the guide exhaust in which the cooling water passage and the oil passage are provided in addition to the exhaust passage becomes complicated, and the attachment / detachment of the catalyst is not easy. For example, another problem arises in that a plurality of catalysts having different functions cannot be arranged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to make it easy to attach and detach a catalyst without complicating the structure of a guide exhaust and to arrange a plurality of catalysts in parallel. It is an object of the present invention to provide an exhaust catalyst device for an outboard motor that can perform the following.

[0009]

In order to achieve the above object, according to the present invention, an exhaust feed passage and an exhaust return passage are formed in a guide exhaust supporting an engine having a crankshaft arranged vertically. In an exhaust catalyst device for an outboard motor configured by disposing a catalyst in the middle of an exhaust passage connected to the exhaust feed passage and the exhaust return passage, an exhaust pipe forming the exhaust passage is independent of the guide exhaust. , And is detachably attached to the guide exhaust.

According to a second aspect of the present invention, in the first aspect of the invention, a plurality of catalysts are arranged in series in the exhaust passage in the exhaust passage.

According to a third aspect of the present invention, in the first or second aspect, an A / F sensor for detecting an air-fuel ratio is disposed upstream of the catalyst in the exhaust passage in the exhaust gas flow direction. It is characterized by.

According to a fourth aspect of the present invention, in the first, second or third aspect, an exhaust gas temperature sensor for detecting an exhaust gas temperature is disposed downstream of the catalyst in the exhaust passage in the exhaust gas flow direction. It is characterized by the following.

According to a fifth aspect of the present invention, in the first to third or fourth aspects of the present invention, the catalyst is arranged at least above the exhaust return passage.

According to the first aspect of the present invention, the exhaust pipe formed independently of the guide exhaust is removably attached to the guide exhaust, and the catalyst is provided in the middle of the exhaust pipe. Can be attached and detached to and from the guide exhaust together with the catalyst without complicating the exhaust pipe, making it easier to attach and detach the catalyst. can do.

According to the second aspect of the present invention, for example, catalysts having different functions can be provided side by side to improve exhaust gas purification performance.

According to the third aspect of the present invention, since the A / F sensor is mounted on the exhaust pipe formed independently of the guide exhaust, the degree of freedom in designing the mounting position of the A / F sensor is increased.

According to the fourth aspect of the present invention, by detecting the temperature downstream of the catalyst with the exhaust gas temperature sensor, it is possible to prevent abnormal temperature rise of the catalyst and to prevent damage to the catalyst.

According to the fifth aspect of the present invention, since the catalyst is arranged at least above the exhaust return passage, water does not reach the catalyst through the exhaust return passage, and the function of the catalyst is inhibited by the water. Nothing. Further, moisture contained in the exhaust gas does not accumulate around the catalyst and does not impair the function of the catalyst.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a side view of an outboard motor equipped with an exhaust catalyst device according to the present invention, FIG. 2 is a plan view of the outboard motor with an upper cowling removed, and FIG. It is a sectional side view of an upper part of an outer machine.

As shown in FIG. 1, the outboard motor 1 according to the present embodiment is detachably attached to a stern plate 100a of a hull 100 by a clamp bracket 2, and is mounted on the clamp bracket 2 by a mount member 3. A swivel bracket 5 that elastically supports the propulsion unit 4 is pivotally mounted on a tilt shaft 6 so as to be vertically rotatable. And
The propulsion unit 4 is rotatably supported in the horizontal direction by a steering shaft (not shown) inserted through the swivel bracket 5, and is rotated left and right by the steering bracket 7.

The propulsion unit 4 has a housing composed of an upper cowling 8, an upper case 9 and a lower case 10, and an upper part of the upper case 9 has an engine 11 as a drive source. And a bottom cowling 13 that covers a lower portion of the engine 11 are attached. The upper cowling (engine case) 8 that covers the upper part of the engine 11 is detachably attached to the bottom cowling 13, and the lower case 10 is attached to the lower part of the upper case 9.
Is attached.

The engine 11 is a water-cooled four-cycle four-cylinder engine. As shown in FIGS. 2 and 3, a crankshaft 15, an intake camshaft 16, and an exhaust camshaft 17 are provided in a cylinder body 14 in a vertical direction. Is pierced.
A drive pulley 18 and a flywheel 19 are fixed to an upper portion of the crankshaft 15, and the intake and exhaust camshafts 16 and 1 are fixed.
Driven pulleys 20 and 21 are fixed to the respective upper ends of 7, and an endless belt 22 is wound around the drive pulley 18 and the driven pulleys 20 and 21.

Therefore, the rotation of the crankshaft 15 is transmitted from the driving pulley 18 to the intake / exhaust camshafts 16 and 17 via the belt 22 and the driven pulleys 20 and 21, and these intake / exhaust camshafts 16 and 17 rotate respectively. Driven.

On the other hand, as shown in FIG. 3, four cylinders 23 are vertically arranged in the cylinder body 14, and a piston 24 which is slidably fitted in each cylinder 23 in a horizontal direction is connected to a connecting rod 25. Are connected to the crankshaft 15 through a cylinder 23 of each piston 24.
The reciprocating linear motion in the inside is converted into a rotational motion of the crankshaft 15 via the connecting rod 25.

In the cylinder head 26 attached to the end of the cylinder body 14, two intake passages (not shown) and two exhaust passages 27 are formed for each cylinder. The exhaust passage 27 is opened and closed at appropriate timing by two intake valves (not shown) and exhaust valves 28 respectively, whereby required gas exchange is performed in each cylinder 23. The intake and exhaust valves 28 are driven by the intake and exhaust camshafts 16 and 17, respectively.

As shown in FIG. 2, a total of four intake pipes 29 connected to each intake passage are connected to the cylinder head 26, and each intake pipe 29 is located in front of the engine 11 (downward in FIG. 2). , And a throttle body 31 is provided in the middle of the silencer 30. In FIG. 2, 32 is an injector, 33 is a fuel pump, 34 is a thermostat, 35 is a starter motor, and 36 is a flywheel cover.

Next, the structure of the exhaust catalyst device according to the present invention will be described with reference to FIGS. FIG. 4 is a view similar to FIG.
FIG. 5 is a sectional view taken along the line BB of FIG. 4, and FIG.
FIG. 7 is an enlarged sectional view taken along line CC of FIG. 4, and FIG. 7 is an enlarged sectional view taken along line DD of FIG.

As shown in FIG.
The two exhaust passages 27 formed in each of the cylinders 6 are joined to an exhaust passage (not shown) vertically penetrating through the cylinder body 14.

On the other hand, the guide exhaust 12
As shown in FIG. 5, an exhaust feed passage 37 bent in a horizontal direction from the upper direction and an exhaust return passage 38 bent in a lower direction from the horizontal direction are formed, and the exhaust feed passage 37 is formed on the upper surface of the guide exhaust 12. Rectangular entrance 3
7a, and opens as an elliptical outlet 37b on the side of the guide exhaust 12. The exhaust return passage 38 opens as an elliptical inlet 38a on the side of the guide exhaust 12, and opens as a rectangular outlet 38b on the lower surface of the guide exhaust 12. The inlet 37 a of the exhaust feed passage 37 is connected to the exhaust passage (not shown) penetrating the cylinder body 14, and the outlet 38 b of the exhaust return passage 38 is formed in the upper case 9 and the lower case 10. It opens to an exhaust passage (not shown).

In this embodiment, as shown in FIG. 3, an exhaust pipe 39 is removably connected to the guide exhaust 12 with bolts or the like in a dead space below the cylinder head 26 of the engine 11. As shown in FIG. 4, the exhaust pipe 39 has a substantially U-shape in plan view and is formed independently (separately) from the guide exhaust 12. One end of the exhaust pipe 39 is the exhaust feed passage 37 of the guide exhaust 12.
The other end is connected to the guide exhaust 1
2 is connected to an inlet 38a of the exhaust return passage 38, and a three-way catalyst 4 is provided in the middle of an exhaust passage 40 formed therein.
1 and the NO _X catalyst 42 are in the exhaust flow direction (the direction of the arrow in the figure).
Are arranged side by side in series.

That is, the exhaust pipe 39 is composed of an exhaust feed pipe 39A, an exhaust return pipe 39B, and a connecting pipe 39C connecting the two, and the three-way catalyst 41 is sandwiched between the exhaust feed pipe 39A and the connecting pipe 39C. is, the NO _X catalyst 42 is held between the connecting pipe 39C and the exhaust return pipe 39B. still,
The cooling water passage 4 is provided on the outer periphery of the exhaust pipe 39 and around the exhaust feed passage 37 and the exhaust return passage 38 of the exhaust guide 12.
3, 44, and 45 are formed respectively (see FIG. 5).

Also, as shown in FIG.
A / F sensor (O ₂ sensor) 4 for detecting an air-fuel ratio upstream of the catalysts 41 and 42 in the exhaust gas flow direction
An exhaust temperature sensor 47 for detecting the exhaust gas temperature is disposed downstream of the catalysts 41 and 42 in the exhaust gas flow direction. Here, the mounting structure of the A / F sensor 46 and the exhaust gas temperature sensor 47 is shown in FIGS. 6 and 7, respectively.

That is, as shown in FIG. 6, the A / F sensor 46 has a screw hole 39 formed on the upper part of the exhaust feed pipe 39A.
The exhaust temperature sensor 47 is inserted from above into a screw hole 39b formed in the upper part of the exhaust return pipe 39B and screwed into the screw hole 39b as shown in FIG. As shown by a chain line in FIG. 4, the A / F sensor 46 and / or the exhaust temperature sensor 47 may be mounted horizontally from the inside of each of the exhaust feed pipe 39A and the exhaust return pipe 39B. If the structure is adopted, interference between the A / F sensor 46 and the exhaust temperature sensor 47 between the upper cowling 8 when the upper cowling 8 is attached and detached can be prevented.

The exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber of each cylinder of the engine 11 is discharged to the exhaust passage 27 of the cylinder head 26 when the exhaust valve 28 is opened during the exhaust stroke. Flows downward through an exhaust passage (not shown) vertically penetrating through the body 14,
As shown by arrows in FIGS. 4 and 5, the air is introduced into the exhaust passage 40 in the exhaust pipe 39 through the exhaust feed passage 37 of the guide exhaust 12. Then, the exhaust gas is exhausted through the exhaust passage 40.
After being cleaned sequentially flows through the three-way catalyst 41 and the NO _X catalyst 42 in the course of flowing, it flows from the exhaust passage 40 to the exhaust return passage 38 of the exhaust guide 12, formed in the upper case 9 and lower case 10 not It is discharged into water through the illustrated exhaust passage.

By the way, in the process where the exhaust gas flows through the exhaust passage 40, the O ₂ of the exhaust gas before flowing through the catalysts 41 and 42 is obtained.
The concentration is detected by the A / F sensor 46, the detection result is fed back, and the amount of fuel injected from the injector 32 (see FIG. 2) is determined to be a predetermined air-fuel ratio (A / F).

The temperature of the exhaust gas passing through the catalysts 41 and 42 is detected by an exhaust gas temperature sensor 47 to warn a driver whose detected exhaust gas temperature exceeds a predetermined value or to automatically lower the engine speed. And the like, the abnormal temperature rise of the catalysts 41 and 42 is prevented, and the damage thereof is prevented beforehand.

As described above, in the present embodiment, the exhaust pipe 39 formed independently of the guide exhaust 12 is detachably attached to the guide exhaust 12, and the two catalysts 41 and 42 are arranged in the middle of the exhaust pipe 12. Was established,
The structure of the guide exhaust 12 is not complicated, and the separate exhaust pipe 39 can be attached to and removed from the guide exhaust 12 together with the catalysts 41 and 42. For this reason, the attachment and detachment of the catalysts 41 and 42 are facilitated, and the plurality of catalysts 4
Even if they are 1, 42, they can be arranged side by side in the exhaust passage 40.

[0039] Also, it is possible to improve the purifying performance of the exhaust gas by juxtaposed different three-way catalyst 41 and the NO _X catalyst 42 of function as in this embodiment. In this embodiment, two types of catalysts having different functions are arranged in parallel. However, a plurality of catalysts having the same function may be arranged in parallel, or one catalyst (for example, three catalysts) as shown in FIG. (Source catalyst) 41 may be provided.

Further, in the present embodiment, since the A / F sensor 46 is mounted on the exhaust pipe 39 formed independently of the guide exhaust 12, the degree of freedom in designing the mounting position of the A / F sensor 46 can be increased. .

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 9 is a side sectional view of the upper part of the outboard motor. In this figure, the same elements as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

In the present embodiment, as shown in FIG. 9, the exhaust pipe 39 is disposed obliquely upward from the guide exhaust 12 toward the rear (to the left in FIG. 9).
Catalyst provided in 9 (e.g., a three-way catalyst and NO _X catalyst) so that 41 is positioned above the exhaust feed passage 37 and the exhaust return passage 38 of the exhaust guide 12.

Therefore, also in the present embodiment, since the exhaust pipe 39 formed independently of the guide exhaust 12 is detachably attached to the guide exhaust 12, and the catalysts 41 and 42 are provided in the exhaust pipe 39. In addition to obtaining the same effects as in the first embodiment, since the catalysts 41 and 42 are disposed above the exhaust feed passage 37 and the exhaust return passage 39 of the guide exhaust 12, water passes through the exhaust return passage 39 to the catalyst. There is also obtained an effect that the water does not reach, the water contained in the exhaust does not accumulate in the catalyst, and the function of the catalysts 41 and 42 is not hindered by the water.

Although the present invention has been described with reference to a form in which the present invention is particularly applied to a four-stroke engine, it is needless to say that the present invention is similarly applicable to a two-stroke engine.

[0045]

As is apparent from the above description, according to the present invention, an exhaust feed passage and an exhaust return passage are formed in a guide exhaust for supporting an engine in which a crankshaft is arranged in a vertical direction. In an exhaust catalyst device for an outboard motor configured by disposing a catalyst in the middle of an exhaust passage connected to an exhaust feed passage and an exhaust return passage, an exhaust pipe forming the exhaust passage is formed independently of the guide exhaust. Since this is detachably attached to the guide exhaust, the catalyst can be easily attached and detached without complicating the structure of the guide exhaust, and a plurality of catalysts can be arranged side by side. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a side view of an outboard motor provided with an exhaust catalyst device according to Embodiment 1 of the present invention.

FIG. 2 is a plan view of the outboard motor including the exhaust catalyst device according to Embodiment 1 of the present invention in a state where an upper cowling is removed.

FIG. 3 is a side sectional view of an upper portion of an outboard motor including the exhaust catalyst device according to Embodiment 1 of the present invention.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a sectional view taken along line BB of FIG. 4;

FIG. 6 is an enlarged sectional view taken along line CC of FIG. 4;

FIG. 7 is an enlarged sectional view taken along line DD of FIG. 4;

FIG. 8 is a view similar to FIG. 4, showing a modification of the exhaust catalyst device according to Embodiment 1 of the present invention.

FIG. 9 is a side sectional view of an upper portion of an outboard motor including an exhaust catalyst device according to Embodiment 2 of the present invention.

[Explanation of symbols]

Reference Signs List 1 outboard motor 11 engine 12 guide exhaust 15 crankshaft 26 cylinder head 37 exhaust feed passage 38 exhaust return passage 39 exhaust pipe 40 exhaust passage 41 three-way catalyst (catalyst) 42 NO _X catalyst (catalyst) 46 A / F sensor 47 exhaust Temperature sensor

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[Procedure amendment]

[Submission date] March 2, 2001 (2001.3.2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

[0011] According to a third aspect of the invention, characterized in the invention of claim 1 or 2, wherein, in the exhaust flow direction upstream of the catalyst of the exhaust passage, in that a sensors for detecting the air-fuel ratio And

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

According to the third aspect of the present invention, the air-fuel ratio is detected by the exhaust pipe formed independently of the guide exhaust .
Because fitted with because of the sensor, the degree of freedom in designing the mounting position of 該Se Nsa is enhanced.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

Also, as shown in FIG.
An A / F sensor ( or O ₂ sensor) 46 for detecting an air-fuel ratio is disposed upstream of the catalysts 41 and 42 in the exhaust flow direction, and the exhaust gas temperature is downstream of the catalysts 41 and 42 in the exhaust flow direction. Exhaust temperature sensor 4 for detecting
7 are arranged. Here, the A / F sensor (or O
FIGS. 6 and 7 show the mounting structure of the _two sensors 46 and the exhaust gas temperature sensor 47, respectively.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

That is, as shown in FIG.
(Or O ₂ sensor) 46 is inserted from above into a screw hole 39a formed in the upper part of the exhaust feed pipe 39A and screwed, and as shown in FIG. 7, the exhaust temperature sensor 47 is connected to the exhaust return pipe 39B. It is inserted from above into a screw hole 39b formed at the top and screwed. In addition, as shown by a chain line in FIG. 4, an A / F sensor (or an O ₂ sensor)
46 or the exhaust temperature sensor 47 or both are connected to the exhaust feed pipe 39
A and the exhaust return pipe 39B may be mounted substantially horizontally from the inside. If this mounting structure is adopted, the A / F sensor (or O ₂
(Sensor) The interference between the upper cowling 8 of the exhaust temperature sensor 47 and the exhaust temperature sensor 47 can be prevented.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

By the way, in the process in which the exhaust gas flows through the exhaust passage 40, the exhaust gas before flowing through the catalysts 41 and 42 can be compared.
For example, the O ₂ concentration is detected by the O ₂ sensor 46, and the detection result is fed back to the injector 3.
2 (refer to FIG. 2), the fuel injection amount is changed to a predetermined air-fuel ratio (A /
F) is determined.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

[0040] Further, in this embodiment, since the fitted with A / F sensor <br/> server (or O ₂ sensor) 46 configured to separate the exhaust pipe 39 and the exhaust guide 12, the A
The degree of freedom in designing the mounting position of the / F sensor (or O ₂ sensor) 46 is increased.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a side view of an outboard motor provided with an exhaust catalyst device according to Embodiment 1 of the present invention.

FIG. 2 is a plan view of the outboard motor including the exhaust catalyst device according to Embodiment 1 of the present invention in a state where an upper cowling is removed.

FIG. 3 is a side sectional view of an upper portion of an outboard motor including the exhaust catalyst device according to Embodiment 1 of the present invention.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a sectional view taken along line BB of FIG. 4;

FIG. 6 is an enlarged sectional view taken along line CC of FIG. 4;

FIG. 7 is an enlarged sectional view taken along line DD of FIG. 4;

FIG. 8 is a view similar to FIG. 4, showing a modification of the exhaust catalyst device according to Embodiment 1 of the present invention.

FIG. 9 is a side sectional view of an upper portion of an outboard motor including an exhaust catalyst device according to Embodiment 2 of the present invention.

[Description of Signs] 1 Outboard motor 11 Engine 12 Guide exhaust 15 Crankshaft 26 Cylinder head 37 Exhaust feed passage 38 Exhaust return passage 39 Exhaust pipe 40 Exhaust passage 41 Three-way catalyst (catalyst) 42 NOX catalyst (catalyst) 46 A / F sensor or O ₂ sensor (air-fuel ratio
Sensor for detecting) 47 Exhaust gas temperature sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F01N 3/28 301 F01N 7/18 7/00 B01D 53/36 B 7/18 B63H 21/26 EF term (Reference) 3G004 AA05 BA06 DA01 DA12 DA25 EA04 FA04 GA01 3G091 AA04 AA17 AA28 AB03 AB04 BA14 BA15 BA19 BA39 CB02 DA01 DA02 DB10 DC01 EA17 EA34 HA08 HA36 HA37 HA47 HB01 4D048 AA06 AA13 AA18 AB05 CA07 CC02 DA02

Claims (5)

[Claims] An exhaust feed passage and an exhaust return passage are formed in a guide exhaust that supports an engine having a crankshaft arranged in a vertical direction, and a catalyst is provided in the middle of an exhaust passage connected to the exhaust feed passage and the exhaust return passage. An exhaust catalyst device for an outboard motor configured by disposing an exhaust pipe forming the exhaust passage independently of the guide exhaust, and detachably attaching the exhaust pipe to the guide exhaust. Outboard motor exhaust catalytic converter. 2. A plurality of catalysts are arranged in series in the direction of exhaust gas in the middle of the exhaust passage.
The outboard motor exhaust catalyst device according to any one of the preceding claims. 3. The exhaust of an outboard motor according to claim 1, wherein an A / F sensor for detecting an air-fuel ratio is arranged upstream of the catalyst in the exhaust flow direction in the exhaust passage. Catalyst device. 4. The ship according to claim 1, wherein an exhaust gas temperature sensor for detecting an exhaust gas temperature is disposed downstream of the catalyst in the exhaust passage direction in the exhaust passage. Exhaust catalyst for external unit. 5. The exhaust catalyst device for an outboard motor according to claim 1, wherein the catalyst is disposed at least above the exhaust return passage.