To simplify fitting and to improve the rigidity of cylinder branch sections of an exhaust manifold by arranging a solid cooling water distributing pipe astride the outer faces of the cylinder branch sections of the exhaust manifold, and providing a fitting section near a cooling water outlet hole formed on the distributing pipe.

A cooling water distributing pipe 26 is arranged astride the outer faces of the cylinder branch sections of the exhaust manifold of a water- cooled two-cycle three-cylinder engine mounted on a surface sailing ship, and the cooling water distributing pipe 26 is formed with pipes 26A-26C having the inner diameters D1-D3 of a cooling water passage S made gradually smaller toward the depth side from the inlet 26a side. The cooling water outlet holes 26r-26t of the cooling water distributing pipe 26 formed on brackets 32A-32C are matched with a water jacket inlet hole 12f respectively, and the brackets 32A-32C are fixed to the cylinder branch sections of the exhaust manifold by bolts via O-rings (a).