A boat propulsion device includes an engine unit, an attachment portion, an electrical component, wiring, a holder, and an engine cover. The engine unit includes an engine, an exhaust pipe, and a coolant passage. The engine includes a crankshaft which extends vertically. The exhaust pipe is connected to the engine. The coolant passage is configured to cool the engine or the exhaust pipe. The attachment portion is provided integrally with the engine unit on the outside of the coolant passage. The electrical component is attached to the attachment portion. The wiring is connected to the electrical component. The holder is connected to the engine unit on the outside of the coolant passage and holds the wiring. The engine cover houses the engine unit, the attachment portion, the electrical component, the wiring, and the holder.