Personal watercraft with engine having exhaust collecting system

1. A personal watercraft equipped with a multi-cylinder engine including an exhaust collecting system configured to discharge an exhaust gas from the engine, the exhaust collecting system comprising:

a plurality of exhaust passages respectively corresponding to a plurality of cylinders provided in the multi-cylinder engine;

an exhaust collecting passage which is located downstream of the plurality of exhaust passages in a flow direction of the exhaust gas and is configured to collect the plurality of exhaust passages;

a water jacket formed at an outer peripheral region of each of the plurality of exhaust passages, for cooling the exhaust gas flowing in the exhaust passages; and

a connecting passage configured to connect at least two of the plurality of exhaust passages and to propagate a flame into the exhaust gas, the flame in the exhaust gas being propagated via the connecting passage.

2. The personal watercraft according to claim 1 , wherein

the connecting passage is formed at upstream end portions of the plurality of exhaust passages.

3. The personal watercraft according to claim 1 , wherein

the connecting passage is formed between the exhaust passages corresponding to cylinders in which ignition occurs in a sequential order.

4. The personal watercraft according to claim 1 , wherein

the connecting passage has a passage cross-sectional area that is in a range of 1% to 7% of a passage cross-sectional area of each of the plurality of exhaust passages.

5. The personal watercraft according to claim 1 , wherein

the exhaust collecting passage includes a plurality of primary exhaust collecting passages into which two of four exhaust passages respectively extending from exhaust ports of four cylinders in the multi-cylinder engine are collected; and a secondary exhaust collecting passage located downstream of the primary exhaust collecting passages, into which two primary exhaust collecting passages are collected.

6. The personal watercraft according to claim 5 , wherein

the exhaust collecting system further includes a water muffler located downstream of the secondary exhaust collecting passage.

7. A personal watercraft equipped with a multi-cylinder engine including an exhaust collecting system configured to discharge an exhaust gas from the engine, the exhaust collecting system comprising:

a plurality of exhaust passages respectively corresponding to a plurality of cylinders provided in the multi-cylinder engine;

an exhaust collecting passage which is located downstream of the plurality of exhaust passages in a flow direction of the exhaust gas and is configured to collect the plurality of exhaust passages;

a water jacket formed at an outer peripheral region of each of the plurality of exhaust passages, for cooling the exhaust gas flowing in the exhaust passages; and

a connecting passage configured to connect at least two of the plurality of exhaust passages;

wherein the plurality of exhaust passages are arranged in close proximity with each other at downstream end portions thereof, and the connecting passage is comprised of a groove formed on a first joint face of the plurality of exhaust passages formed at the downstream end portions thereof and a second joint face joined to the first joint face.

8. The personal watercraft according to claim 7 , wherein

the connecting passage is formed to extend over the plurality of exhaust passages to provide fluid communication among all of the plurality of exhaust passages.

9. A personal watercraft equipped with a multi-cylinder engine including an exhaust collecting system configured to discharge an exhaust gas from the engine, the exhaust collecting system comprising:

a plurality of exhaust passages respectively corresponding to a plurality of cylinders provided in the multi-cylinder engine;

an exhaust collecting passage which is located downstream of the plurality of exhaust passages in a flow direction of the exhaust gas and is configured to collect the plurality of exhaust passages;

a water jacket formed at an outer peripheral region of each of the plurality of exhaust passages, for cooling the exhaust gas flowing in the exhaust passages; and

a connecting passage configured to connect at least two of the plurality of exhaust passages;

wherein the exhaust passages are arranged in close proximity with each other at downstream end portions thereof, and the connecting passage is formed on a gasket disposed between a first joint face of the plurality of exhaust passages formed at the downstream end portions thereof and a second joint face joined to the first joint face.

10. A personal watercraft equipped with a multi-cylinder engine including an exhaust collecting system configured to discharge an exhaust gas from the engine, the exhaust collecting system comprising:

a plurality of exhaust passages respectively corresponding to a plurality of cylinders provided in the multi-cylinder engine;

an exhaust collecting passage which is located downstream of the plurality of exhaust passages in a flow direction of the exhaust gas and is configured to collect the plurality of exhaust passages;

a water jacket formed at an outer peripheral region of each of the plurality of exhaust passages, for cooling the exhaust gas flowing in the exhaust passages; and

a connecting passage configured to connect at least two of the plurality of exhaust passages;

wherein the exhaust passages compose exhaust manifold inside of which the plurality of exhaust passages are separately provided, and which forms at a downstream end portion thereof a collecting pipe structure into which the separate exhaust passages are arranged in close proximity with each other;

wherein the exhaust collecting passage has at an upstream end portion thereof a collecting pipe structure conforming in shape to the downstream end portion of the exhaust manifold so as to be coupled to the downstream end portion of the exhaust manifold, and at a downstream end portion thereof a collecting passage structure in which the exhaust passages are collected into a common exhaust passage; and wherein

the connecting passage is formed at a joint portion at which the exhaust manifold and the exhaust collecting passage are joined to each other.