In a boat propulsion device, a head portion of an engine includes plug holes, first attachment portions, and a second attachment portion. The plug holes are aligned vertically and parallel or substantially parallel to a crankshaft. The first attachment portions are arranged on the periphery of the plurality of plug holes. The first attachment portions are configured to attach a plurality of ignition coils which are respectively integrated with spark plugs in a coil-on-plug configuration. A second attachment portion is provided separately from the first attachment portions. The second attachment portion is configured to attach an ignition coil connected to the spark plugs in a double ended ignition coil configuration via cables.