JPH08268389A - Cooling structure for exhaust device of surface boat - Google Patents

Abstract

PURPOSE: To prevent a rubber hose from being excessively heated by reducing the volume of cooling water flowing to a water lock and keeping exhaust resistance at a small value. CONSTITUTION: A duplex tube with cooling water flowing inside, is laid at two positions upstream and downstream of an exhaust tube member 14. Duplex tubes so laid are communicated to each other via a cooling water pipe 29. Also, the downstream duplex tube is inclined to have a downward slope. Furthermore, cooling water is discharged to a rubber hose 15 extended approximately horizontally from a joint with the member 14, from the right and left portions of an exhaust passage viewed from the upstream side thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling structure for an exhaust system for a watercraft, in which an exhaust pipe in the vicinity of an engine is water-cooled as a double pipe structure and exhaust gas and cooling water are flowed to a water lock through a common rubber hose. It is a thing.

[0002]

2. Description of the Related Art Conventionally, a watercraft is equipped with a water jet propulsion device which uses a two-cycle engine as a power source, and an occupant straddles a seat on the hull and grips a steering handle to travel. There is something. Since the exhaust system used for this type of watercraft is not expected to be cooled by the wind when traveling due to the fact that it is housed inside the hull,
It was cooled by the engine cooling water.

In cooling the exhaust system with cooling water in this way, the expansion section connected to the engine has a double pipe structure consisting of an inner pipe and an outer pipe, and the cooling water is caused to flow between these pipes. The cooling water is discharged to the exhaust passage at the downstream end of the expansion section. The cooling water discharged to the exhaust passage is passed through a rubber hose connected to the expansion section and flows into the water lock together with the exhaust gas, and then extends upward from the water lock and then extends downward. It was discharged to the propeller chamber of the water jet propulsion device through the exhaust pipe of.

The water lock is for preventing water from flowing back from the exhaust outlet on the propeller chamber side to the engine side when the hull capsizes, and exhausts when the cooling water is accumulated in the exhaust expansion chamber to some extent. It was configured to be pushed out to the exhaust pipe by the pressure of gas.

[0005]

However, the flow rate of the cooling water has been a problem in adopting the structure in which the cooling water is pushed out from the water lock by the pressure of the exhaust gas as described above. That is, as the flow rate of the cooling water increases, the cooling water is pushed out of the water lock more frequently, and the exhaust resistance increases, which hinders the increase of the engine output.

Incidentally, such a problem can be solved by not discharging the cooling water into the exhaust passage. However, in this case, the rubber hose which connects the expansion part and the water lock is cooled by the cooling water. You will not be able to do it. Since the rubber hose is used to prevent the vibration of the engine from being transmitted to the water jet propulsion device and the hull via the exhaust system, it cannot be replaced with a rigid body such as a pipe material. Moreover, considering cost, it is not possible to replace it with an expensive metal bellows hose.

The present invention has been made in order to solve such a problem, and it is possible to prevent the rubber hose from being excessively heated while suppressing the cooling water flowing in the water lock to reduce the exhaust resistance. The purpose is to

[0008]

According to a first aspect of the present invention, there is provided a cooling structure for an exhaust system for a marine vessel, wherein a double pipe section through which cooling water flows is provided at two positions, an upstream side and a downstream side of an exhaust pipe member. At the same time, these double pipes are communicated with each other by a cooling water pipe, and a cooling water outlet for communicating the cooling water passage with the exhaust passage in a state where the passage cross-sectional area is narrowed to the downstream end of the downstream double pipe portion. And a rubber hose is connected so as to cover the cooling water outlet.

According to a second aspect of the present invention, there is provided a cooling structure for an exhaust system for a water traveling vessel according to the first aspect of the present invention, wherein the double pipe portion on the downstream side of the exhaust pipe member has a downward slope. The structure is such that the cooling water is discharged from the left and right sides of the exhaust passage in the rubber hose that extends substantially horizontally from the connection with the exhaust pipe member. It is a thing.

According to a third aspect of the present invention, there is provided a cooling structure for an exhaust system for a marine vessel, wherein a single pipe portion is provided on a downstream side of a double pipe portion of an exhaust pipe member, and an exhaust passage located downstream of the single pipe portion. The cooling water of the double pipe portion is configured to be discharged almost entirely through the cooling water pipe, and a temperature sensor for detecting the temperature of the wall surface of the exhaust passage is attached to the single pipe portion.

[0011]

According to the first aspect of the present invention, since the flow passage of the cooling water has a small passage cross-sectional area between the inlet of the cooling water pipe and the cooling water outlet of the downstream side double pipe portion, the cooling water flowing into the water lock is prevented. Decrease.

According to the second aspect of the invention, the cooling water discharged from the cooling water outlet of the downstream double pipe portion into the rubber hose is pushed by the exhaust gas and the flow rate of the exhaust gas is relatively increased. Flows above.

According to the third aspect of the present invention, since the flow passage of the cooling water has a small passage cross-sectional area at the inlet of the cooling water pipe, the cooling water flowing into the water lock is reduced. Further, since the single pipe portion is difficult to be cooled by the cooling water, the temperature sensor detects the accurate temperature of the exhaust pipe member.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a side view of a watercraft that employs a cooling structure for an exhaust system according to the present invention, in which the water jet propulsion device is cut away. FIG. 2 is a plan view showing a schematic configuration of a watercraft, FIG.
Is a cross-sectional view of the exhaust pipe member according to the present invention, FIG. 4 is a right side view showing a state in which the downstream end of the exhaust pipe member is viewed from the right side of the hull,
5 is a view on arrow A in FIG. 4, and FIG. 6 is VI- in FIG.
FIG. 6 is a sectional view taken along line VI.

In these drawings, reference numeral 1 is a surface-traveling ship according to the present embodiment, and 2 is a hull of the surface-traveling ship 1. In this watercraft 1, an occupant sits astride a seat 3 on a hull 2 and grips a steering handle 4 provided in front of the seat 3 to travel. In addition, steps (not shown) for placing the feet of an occupant are integrally formed with the hull 2 on both left and right sides of the seat 3.

Inside the hull 2, an engine room 6 is provided on the front side of a bulkhead 5 standing on the bottom 2b of the ship, and a pump room 7 is provided on the rear side thereof. An engine 8 is mounted in the engine compartment 6 below the seat 3 and in the center of the hull 2 in the left-right direction, and a fuel tank 9 is arranged in front of the engine 8.

The engine 8 is of a two-cycle, two-cylinder type and has a structure in which two cylinders are arranged in front and rear, and is connected to a jet pump 10 provided at the rear of the hull. The engine 8 and the jet pump 10 make up a water jet propulsion device that drives the watercraft 1.

The engine 8 has an intake device 11 connected to the right side of the hull of a crankcase 8a as shown in FIG. 2, and an exhaust device 12 connected to the left side of the hull of a cylinder body 8b (FIG. 1). The intake device 11 includes a crankcase 8
It has a structure in which a vaporizer (not shown) is connected to a via an intake pipe (not shown), and an intake silencer 11a is further connected to the upstream end of the vaporizer.

The exhaust device 12 includes a cylinder body 8b.
And a lead-out portion 13 that extends the exhaust passage laterally by connecting to the front end of the lead-out portion 13. An exhaust pipe member 14 that extends to the inside of the exhaust pipe member 14 and forms an exhaust expansion chamber therein; and a water lock 16 that is disposed at the bottom of the ship on the left side of the hull and communicates with a rear end of the exhaust pipe member 14 via a rubber hose 15. The jet pump 10 extends upward from the upper rear end of the water lock 16.
Of the exhaust gas of the engine 8 and the exhaust pipe 17 that extends across the upper part of the jet pump 10 and extends rearward and downward on the right side of the hull from the jet pump 10 and is connected to the side wall of the propeller chamber at the rear end of the jet pump 10. The pump 10 has a structure in which it is discharged into the propeller chamber from an exhaust outlet 10a which is opened on the side wall of the propeller chamber.

Since the exhaust device 12 is housed in the hull 2 and cannot be expected to be cooled by wind during traveling, it has a structure for cooling with engine cooling water. That is, as shown in FIG. 3, the exhaust pipe member 14 has a double pipe structure to supply engine cooling water between the inner pipe portion and the outer pipe portion thereof, and the exhaust pipe member 14 exhausts the exhaust gas in the rubber hose 15 from the exhaust pipe member 14. The passage is cooled by discharging the cooling water into the passage. The cooling water discharged to the rubber hose 15 flows into the water lock 16 and is accumulated in the water lock 16 to some extent, and then is pushed out to the exhaust pipe 17 by the pressure of the exhaust gas and is discharged into the propeller chamber together with the exhaust gas. It The exhaust device 12 of the present embodiment has the same structure as the conventional structure on the downstream side from the rubber hose 15.

Here, the structure of the exhaust pipe member 14 will be described in detail. The exhaust pipe member 14 includes an upstream pipe member 18 connected to the lead-out portion 13, and a downstream side pipe connected to the downstream end portion of the upstream pipe member 18 via a connecting pipe member 19 and a connecting outer pipe 20. The pipe 21 and the downstream outer pipe 22 and a seal rubber 23 fixed to the downstream end of the downstream outer pipe 22.

The upstream pipe member 18 integrally forms an inner pipe portion 18a and an outer pipe portion 18b by, for example, a lost wax method, and a cooling water passage W1 is provided between these both portions.
Is formed, and is formed in a substantially lateral U-shape in a side view so as to be convex toward the front side of the hull. Further, in the upstream pipe member 18, the lower end portion is connected to the lead-out portion 13 so that the exhaust passage S1 in the inner pipe portion 18a communicates with the exhaust passage (not shown) of the lead-out portion 13 and the cooling water is provided. Passage W1
Are formed so as to communicate with a cooling water outlet (not shown) of the outlet 13. The downstream end of the upstream pipe member 18 is formed so as to be directed obliquely rearward and downward.

The connecting pipe member 19 is formed by integrally forming an inner pipe portion 19a and an outer pipe portion 19b, and the upstream end of the inner pipe portion 19a is connected to the inner pipe portion 18a of the upstream pipe member 18. Is connected to the outer tube portion 19 via a connecting band 24.
the upstream end of b is the outer pipe portion 18b of the upstream pipe member 18.
To the outer tube 20 for connection. The outer pipe 20 for connection is formed by connecting a metal pipe body 20b on the downstream side to a rubber pipe body 20a on the upstream side, and the upstream end of the rubber pipe body 20a is connected to the upstream side pipe member 18 Outer tube part 1
8b, and the downstream end of the metallic pipe body 20b is bolted to the outer pipe portion 19b of the connecting pipe member 19 by a connecting bolt 25.

With such a structure, the upstream pipe member 18
The cooling water passage W2 communicating with the cooling water passage W1 is formed inside the outer pipe portion 19b of the connecting pipe member 19 and the connecting outer pipe 20. In addition, the inner pipe portion 1 of the connecting pipe member 19
The exhaust passage S communicating with the exhaust passage S1 is provided inside 9a.
Forming 2. The pilot water hose 2 is provided at the highest position in the cooling water passage W2 via a cooling water extraction pipe 26 integrally formed with the rubber pipe body 20a.
One end of 7 is connected. The other end of this hose 27 is connected to a pilot water discharge port (not shown) on the side wall of the hull 2.

That is, when the uppermost part of the cooling water passage W2 is filled with the cooling water, a part of the cooling water in the cooling water passage W2 passes through the hose 27 and is discharged out of the pilot water discharge port. become. Therefore, the occupant can visually confirm that the cooling water is supplied to the cooling water system with such a water amount as to reach the uppermost portion of the exhaust pipe member 14.

The downstream inner pipe 21 is formed by integrally forming a connecting flange 21a located at the upstream end and a pipe portion 21 having a circular cross section extending downstream from the connecting flange 21a. Is inserted from the upstream side into the downstream side outer pipe 22. Then, the downstream end face of the connecting flange 21a is brought into close contact with the upstream end face of the downstream outer pipe 22, and the pipe portion 2
The outer peripheral portion of the downstream side of 1b is the inner step portion 22 of the outer pipe 22 on the downstream side.
It is fixed to the connecting pipe member 19 by the connecting bolt 25 in a state of being closely attached to a through a seal member 28. The connecting bolt 25 is used for the connecting outer tube 2
No. 0 metal pipe body 20b, the connection pipe member 19, and the connection flange 21a are penetrated and screwed to the downstream outer pipe 22.

Further, the connecting flange 21a is provided with a number of through holes 21c which are open at the upstream end surface and the downstream end surface and are spaced apart in the circumferential direction of the connecting flange 21a. Further, the downstream end of the downstream inner pipe 21 extends downstream of the seal member 28, and is formed so that the opening diameter is smaller than the inner diameter of the pipe portion 21b upstream thereof.

By thus connecting the downstream inner pipe 21 and the downstream outer pipe 22 to the connecting pipe member 19,
The cooling water passage W2 has a through hole 21 for the connecting flange 21a.
A cooling water passage W3 that communicates via c is formed between the two pipes 21 and 22. At the same time, an exhaust passage S3 communicating with the exhaust passage S2 is formed inside the downstream side inner pipe 21. The cooling water passages W2, W3 and the exhaust passages S2, S3 described above are connected to a downstream end portion of the upstream pipe member 18 which is formed so as to be directed obliquely rearward and downward, and a connecting pipe member and a connecting outer pipe 20. Further, since it is formed by connecting the downstream inner pipe 21 on the same axis in this order, it extends rearward and downward as shown in FIG.

A communication passage for communicating the cooling water passage W3 with a space (exhaust passage communicating with the exhaust passage S3) downstream of the sealing member 28 is provided at the downstream end of the downstream inner pipe 21. 21d is formed. This communication passage 21d
Has one end open to the outer peripheral surface which is the wall surface of the cooling water passage W3 in the pipe portion 21b of the downstream inner pipe 21, and the other end is the pipe portion 21b.
The outer peripheral surface of the portion of b that extends downstream from the seal member 28 is open toward the downstream side in the exhaust flow direction.

The downstream side outer pipe 22 is inclined such that the downstream side end portion thereof gradually extends downward as it goes downstream from the portion corresponding to the downstream end of the downstream side inner pipe 21. A substantially cylindrical inner pipe portion 22b is integrally formed inside the downstream end so as to have a double pipe structure. The rubber hose 15 is fitted and fixed to the outer peripheral surface of the downstream end. As shown in FIG. 1, the rubber hose 15 is bent substantially from the connection portion with the downstream outer pipe 22 and extends substantially horizontally toward the rear of the hull 2.

A space having an annular cross-section opening downward is formed between the outer peripheral surface of the inner pipe portion 22b and the inner peripheral surface of the outer peripheral portion of the downstream outer pipe 22. The seal rubber 23 is press-fitted and fixed to the downstream end of the downstream outer pipe 22 so as to close the opening of this space. Further, this space communicates with the cooling water passage W3 via a cooling water pipe 29 connected to the downstream outer pipe 22.

As shown in FIGS. 4 and 5, the cooling water pipe 29 has its front end connected to the lower portion of the downstream outer pipe 22 which corresponds to the downstream end of the cooling water passage W3 and is on the right side of the hull. Then, the rear end is connected to a portion of the downstream outer pipe 22 corresponding to the upper portion of the space and on the rear side of the hull. Thereby, the space communicated with the cooling water passage W3 becomes the cooling water passage W4. The center side of the cooling water passage W4 having an annular cross section has the downstream inner pipe 21.
An exhaust passage S4 communicates with the internal exhaust passage S3.

In FIG. 3 to FIG. 5, a temperature sensor is provided on the outer peripheral portion of the downstream side outer pipe 22 on the right side of the hull. The temperature sensor 30 detects the temperature of a part of the downstream outer pipe 22 corresponding to the downstream end of the downstream inner pipe 21 (a part where the cooling water passage is not formed) and outputs a temperature signal to a warning device (not shown). Is output. This warning device, when the temperature of the downstream side outer pipe 22 detected by the temperature sensor 30 reaches a preset temperature,
A warning light (not shown) provided in the vicinity of the steering handle 4 is configured to be turned on. The set temperature is
The temperature is set to be slightly lower than the limit temperature of use of the rubber hose 15.

The seal rubber 23 is made of a rubber material and has an annular cross section as shown in FIG. 6, and two recessed grooves 23a extending along the axial direction of the seal rubber 23 are formed at two locations on the outer peripheral portion. ing. These recessed grooves 23a are arranged in the left and right sides of the exhaust passage S4 when viewed from the upstream side. That is, the cooling water passage W4 has these concave grooves 2
The exhaust passage S4 and the inner space of the rubber hose 15 are communicated with each other via the 3a.

As described above, the exhaust pipe member 14 has double pipes at two positions, from the upstream end to the downstream end of the downstream inner pipe 21 and inside the downstream end of the downstream outer pipe 22. The double pipe portions are connected by a cooling water pipe 29. Further, the temperature sensor 30 is attached to a single pipe portion of the downstream outer pipe 22 which is located between the double pipe portions.

That is, in the exhaust device 12 having the exhaust pipe member 14, the exhaust gas of the engine 8 flows into the exhaust passage S1 from the engine-side lead-out portion 13, and the exhaust passages S1 to S1.
It expands in the exhaust pipe member 14 by passing through S4 in this order, and then the rubber hose 15 → water lock 16 →
It is discharged into the propeller chamber from the exhaust outlet 10a through an exhaust system called an exhaust pipe 17.

The cooling water flowing from the engine-side outlet 13 into the cooling water passage W1 of the exhaust pipe member 14 flows into the cooling water passage W3 from the cooling water passage W1 through the cooling water passage W2 and the through hole 21c. Then, from here, substantially the entire amount flows into the cooling water passage W4 via the cooling water pipe 29. A part of the cooling water in the cooling water passage W3 flows out into the single pipe portion of the downstream outer pipe 22 (in the exhaust passage S4) through the communication passage 21d provided in the downstream inner pipe 21. This cooling water hits the inner surface of the single pipe portion on the downstream side of the portion corresponding to the temperature sensor 30 and cools it.

The cooling water flowing from the cooling water pipe 29 into the cooling water passage W4 passes through the concave groove 23a of the seal rubber 23 and is discharged into the exhaust passage. By discharging the cooling water into the exhaust passage in this manner, the rubber hose 15 is cooled from the inner surface.

Therefore, when the above-described exhaust pipe member 14 is used, the flow path of the cooling water is the inlet of the cooling water pipe 29 and the concave groove 23.
Since the cross-sectional area of the passage becomes smaller at the inlet of a, the cooling water discharged to the rubber hose 15 and flowing into the water lock 16 decreases.

Further, the downstream double pipe portion which becomes the cooling water passage W4 is inclined so as to extend downward as it goes downstream, and the rubber hose 15 is connected to the double pipe portion. Since the cooling water is discharged from the left and right sides of the rubber hose 15 by the concave groove 23a of the seal rubber 23, the cooling water discharged from the concave groove 23a into the rubber hose 15 is exhausted. By being pushed by the gas, the flow rate of the exhaust gas in the rubber hose 15 flows to a portion where the flow rate is relatively large, that is, the inner surface that is the upper side of the bent portion. The position of the inner surface on the upper side of this bent portion is indicated by reference numeral 15a in FIG.
Indicated by For this reason, even if the configuration that regulates the flow rate of the cooling water is adopted as described above, the cooling water will efficiently flow to the portion of the rubber hose 15 that is likely to reach a high temperature.

Further, since the portion of the single pipe portion of the downstream outer pipe 22 to which the temperature sensor 30 is attached is difficult to be cooled by the cooling water, the temperature sensor 30 can detect the accurate temperature of the downstream outer pipe 22. . As a result, the temperature of the rubber hose 15 can be indirectly and accurately determined based on the output of the temperature sensor 30.

[0042]

As described above, in the cooling structure of the exhaust device for a watercraft according to the first aspect of the present invention, the double pipe section through which the cooling water flows is provided at two locations, the upstream side and the downstream side of the exhaust pipe member. Cooling water that connects these double pipes to each other through a cooling water pipe, and connects the cooling water passage to the exhaust passage with the passage cross-sectional area narrowed at the downstream end of the downstream double pipe portion. Since an outlet was provided and a rubber hose was connected so as to cover this cooling water outlet, the passage of the cooling water has a small passage cross-sectional area between the inlet of the cooling water pipe and the cooling water outlet of the downstream double pipe section. The cooling water flowing into the lock is reduced. For this reason, the cooling water is not frequently pushed out from the water lock, so that the exhaust resistance becomes smaller than in the conventional case, and the output of the engine can be increased.

A cooling structure for an exhaust system for a watercraft according to a second aspect of the present invention is the cooling structure for an exhaust system for a watercraft according to the first aspect, wherein the double pipe portion on the downstream side of the exhaust pipe member has a downward gradient. The structure is such that the cooling water is discharged from the parts on both the left and right sides when viewed from the upstream side of the exhaust passage into the rubber hose that extends in a substantially horizontal direction from the connection part with this exhaust pipe member. The cooling water discharged into the rubber hose from the cooling water outlet of the downstream double pipe portion is pushed by the exhaust gas and flows to the upper side of the bent portion where the flow rate of the exhaust gas is relatively large. For this reason, the cooling water efficiently and substantially evenly flows to the portion of the rubber hose that is likely to reach a high temperature, so that the temperature rise can be suppressed even if the cooling water is small.

In the cooling structure of the exhaust device for a water traveling vessel according to the third aspect of the invention, a single pipe portion is provided on the exhaust pipe member downstream of the double pipe portion, and the exhaust passage is located downstream of the single pipe portion. Since the cooling water in the double pipe section is configured to be discharged almost entirely through the cooling water pipe, the flow passage of the cooling water has a small passage cross-sectional area at the inlet of the cooling water pipe, and the cooling water flowing into the water lock is reduced. Thus, the output of the engine can be increased as in the first aspect of the invention.

Further, since the temperature sensor for detecting the temperature of the wall surface of the exhaust passage is attached to the single pipe portion, it is difficult for the single pipe portion to be cooled by the cooling water, so that the temperature sensor can detect the accurate temperature of the exhaust pipe member. You can Therefore, the temperature of the rubber hose can be determined accurately based on the output of the temperature sensor even though it is indirect.Therefore, the cooling water flowing through the rubber hose can be reduced as described above, and sand such as sand in the cooling water system can be reduced. Even if foreign matter is accumulated and the flow rate of the cooling water is further reduced, some warning can be issued before the rubber hose reaches the use limit temperature.

[Brief description of drawings]

FIG. 1 is a side view of a watercraft that employs a cooling structure for an exhaust system according to the present invention, in which the water jet propulsion device portion is cut away.

FIG. 2 is a plan view showing a schematic configuration of a watercraft.

FIG. 3 is a cross-sectional view of an exhaust pipe member according to the present invention.

FIG. 4 is a right side view showing a state where the downstream end of the exhaust pipe member is viewed from the right side of the hull.

5 is a view on arrow A in FIG. 4. FIG.

6 is a sectional view taken along line VI-VI in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Watercraft, 2 ... Hull, 8 ... Engine, 12 ... Exhaust device, 14 ... Exhaust pipe member, 15 ... Rubber hose, 16 ... Water lock, 18 ... Upstream pipe member, 19 ... Connection pipe member, 20 ... Connection outer pipe, 21 ... Downstream inner pipe, 22 ... Downstream outer pipe, 22b ... Inner pipe portion, 23 ... Seal rubber, 23
a ... concave groove, 29 ... cooling water pipe.

Claims (3)

[Claims] 1. A cooling water passage having a double pipe structure is provided with an exhaust pipe member formed around an exhaust passage, and the cooling water of the double pipe portion is discharged into the exhaust passage to provide cooling water and exhaust gas. In the cooling structure of an exhaust device for a watercraft that allows gas to flow from an exhaust pipe member to a water lock via a rubber hose, the double pipe portion is provided at two locations, an upstream side and a downstream side of the exhaust pipe member. The heavy pipe parts are connected to each other by a cooling water pipe formed separately from the exhaust pipe member, and the cooling water passage is exhausted to the downstream end of the downstream double pipe portion with the passage cross-sectional area narrowed. A cooling structure for an exhaust device for a watercraft, wherein a cooling water outlet communicating with the passage is provided, and the rubber hose is connected so as to cover the cooling water outlet. 2. The cooling structure for a watercraft exhaust system according to claim 1, wherein the downstream double pipe portion of the exhaust pipe member is inclined so as to gradually extend downward toward the downstream side, The cooling water outlets that connect the downstream double pipe section and the exhaust passage are arranged at the left and right sides of the exhaust passage as viewed from the upstream side, and the rubber hose is bent from the connection portion with the exhaust pipe member. A cooling structure for an exhaust system for a watercraft, which is characterized by being extended substantially horizontally. 3. A double pipe structure is provided with an exhaust pipe member in which a cooling water passage is formed around an exhaust passage, and the cooling water of the double pipe portion is discharged into the exhaust passage to provide cooling water and exhaust gas. In a cooling structure of an exhaust device for a watercraft that flows gas from the exhaust pipe member to a water lock via a rubber hose, a single pipe portion is provided on the downstream side of the double pipe portion of the exhaust pipe member, and a single pipe portion is provided downstream from the single pipe portion. The cooling water of the double pipe part is discharged to the exhaust passage located on the side through a cooling water pipe formed separately from the exhaust pipe member, and the temperature of the exhaust passage wall surface is detected in the single pipe part. A cooling structure for an exhaust system for a marine vessel, which is equipped with a temperature sensor.