An outboard engine structure is provided including an engine mounted in an upper portion of the structure, wherein an exhaust gas from the engine is passed through an exhaust passage located vertically within an engine body case, into a lower portion of the case and discharged into water. A catalytic converter is positioned adjacent an oil pan the said engine. The oil pan is mounted in a suspended manner in an upper area within the engine body case and the catalytic concerted is incorporated in the middle of the exhaust passage. The catalytic converter is fixed to and supported on the oil pan. Thus, it is easy to place the catalytic converter in the engine body case.