| 摘要 |
PROBLEM TO BE SOLVED: To reduce weight and to impede deformation of lateral side walls by providing a rib inside an upper easing, and fixing the left end of the rib to the inner surface of the left side wall of the upper casing, while fixing the right end to the inner surface of the right side wall. SOLUTION: An upper casing 3 of an outboard motor has a rib 28 laid between a left side wall 3a and a right side wall 3b. This rib 28 can impede space enlargement and contraction and flexure of the left and right side walls 3a, 3b to the utmost even if the internal pressure of the upper casing 3 fluctuates due to exhaust gas and the like. Furthermore, this rib 28 is vertically extended so as to prevent deformation over a relatively large vertical range of the upper casing 3. The rigidity of the upper casing 3 can therefore be enhanced without thickening the side walls 3a, 3b. As a result, resonance of the upper casing 3 is prevented to prevent the generation of large vibrating sound. |
