Water-cooled engine

A water-cooled engine comprising:

• a cylinder having a combustion chamber;
• a cylinder head;
• an exhaust manifold;
• a combustion chamber water jacket formed around the combustion chamber and having a cooling water outlet in its upper portion;
• a cylinder-head water jacket formed around the cylinder head;
• an exhaust manifold water jacket formed around the exhaust manifold;
• a water passage;
• and
• a cooling water passage;
• wherein
• the water passage connecting an inlet of the exhaust manifold water jacket and an inlet of the cooling water passage;
• an outlet of the exhaust manifold water jacket being connected to a lower portion of the combustion chamber water jacket;
• and
• an outlet of the cooling water passage being connected to the cylinder-head water jacket.

A water-cooled engine comprising:

• a cylinder having a piston slidably received in the cylinder to define a portion of a combustion chamber;
• a cylinder head;
• an exhaust manifold;
• a cylinder-block water jacket formed around the combustion chamber;
• a cylinder-head water jacket formed around the cylinder head;
• a cooling water supply passage;
• and
• a water passage defined by a pipe located outside a side face of the cylinder;
• wherein
• an outlet of the cooling water supply passage is connected to the cylinder-head water jacket;
• and
• the water passage provides cooling water which has cooled a higher-temperature portion of the engine to the cylinder-block water jacket.