Personal watercraft and engine mounted in personal watercraft

A jet-propulsion personal watercraft equipped with an engine including a crankshaft extending along a longitudinal direction of a body of the watercraft and having a rear end portion for taking out an output from the engine, and an air-intake passage and an exhaust passage extending inside a cylinder head along a lateral direction of the body, the engine comprising:

• a cylinder head cover provided over the cylinder head;
• an ignition plug attached to the cylinder head;
• a penetrating hole formed to extend from an upper surface of the cylinder head cover to a lower surface of the cylinder head through the cylinder head cover and the cylinder head, for accommodating and attaching the ignition plug inside thereof, the penetrating hole including a step portion axially supporting the ignition plug, and a screw portion extending downwardly from the step portion to open in the lower surface of the cylinder head, for fixing the ignition plug;
• a connecting member connected to an upper end of the ignition plug and located inside the penetrating hole, for connecting a power supply to the ignition plug that activates the ignition plug;
• a closing member for creating a seal between the connecting member and the penetrating hole;
• and
• an air hole formed to extend obliquely downward from a vicinity of the step portion so as to communicate with an outside of the cylinder head.