Abstract: A starter for an engine, having a ring gear includes an output shaft for slidably holding a pinion gear engageable with the ring gear, a housing having an opening portion that enables the pinion gear to engage with the ring gear when the pinion gear advances, a cover having a shutter, a front wall and a side wall for sliding together with the pinion gear. The shutter opens the opening portion when the pinion gear advances and shuts the most part of the opening portion when the pinion gear retracts. The front wall is provided to cover at least half of a front portion, which faces to the ring gear, of the pinion gear. The side wall is extended from the front wall in a direction parallel to an axis of the output shaft to cover at least half of the gear tooth periphery in a circumferential direction of the pinion gear. When water carried by the rotating ring gear comes to the opening portion when the pinion gear rotates with the ring gear, most of such water is blocked by the gear tooth.