PURPOSE: To facilitate mounting and removing work by dividing an engine cowling into three parts of a center cowling in the center and side cowlings in both sides and mounting the side cowlings being able to open and close to the center cowling.

CONSTITUTION: An engine 13 is coated almost in its total side surface part and upper surface part with a top cowling 18 divided into three parts of a center cowling 19 in the central part in the longitudinal direction and side cowlings 20, 21 in both sides in the longitudinal direction, and weight of each cowling is decreased when it is removed. The center cowling 19 is connected by a bolt to the upper part of an engine body 13A by longitudinally extending two stays while connecting by a bolt 23 the lower both side parts. The side cowlings 20, 21 are fixed by a rubber band 25 to both sides of the center cowling 19 through a seal member 24. The rubber band 25 is fixed in its one end by a supporting bolt of the side cowlings 20, 21 with the other and engaged with and disengaged from a hook of the center cowling 19. Accordingly, work of mounting, removal and maintenance can be facilitated.