An engine for a planing-type boat can have a water jacket, which is provided in a main body of the engine and which is supplied with cooling water for cooling the engine. The water jacket can include a ceiling with its rearward portion higher than its forward portion. The water jacket can also include a water drain provided at the rear highest portion of the ceiling to discharge cooling water out of the water jacket. In addition, a head bolt fastening portion for receiving a bolt is provided on an outer side portion of the water jacket in the cylinder head, and a rib is provided in a portion of the water jacket that corresponds to the head bold fastening portion.