Abstract: An engine unit includes a cylinder block of a short-skirt type which has a plurality of first partition walls and a plurality of crank journals formed on the partition walls and rotatably receiving the crankshaft. Bearing caps are fitted to the crank journals and rotatably hold the crankshaft in cooperation with the crank journals. A lower case is fixed to the cylinder block and covers the crankshaft. The lower case includes a pair of flanges abutting against the lower edges of the skirt portions, a semi-cylindrical bottom wall, and a plurality of second partition walls formed on the bottom wall to oppose the first partition walls. Each bearing cap is clamped between the first and second partition walls. The lower case is fixed to the cylinder block by means of first bolts screwed into the skirt portions through the flanges, and second bolts screwed into the crank journals through the second partition walls and bearing caps.