Engine and saddle type vehicle

An engine includes a piston and a casing including a cylinder. The cylinder houses the piston. The cylinder and the piston forms a combustion chamber. The casing has as intake port, a plurality of exhaust ports, a spark plug hole, a drainage hole, and a water jacket. The spark plug hole extends to the combustion chamber. A spark plug is housed in the spark plug hole. The drainage hole extends from the spark plug hole. The water jacket includes a central passage and an inter-port passage. The central passage is near the spark plug hole. The inter-port passage extends to the central passage. The inter-port passage is formed between the plurality of exhaust ports. The inter-port passage is located between the drainage hole and the cylinder in a central axis direction of the spark plug hole.