Outboard – a detachable motor fixed to the transom
Inboard/Outboard, Stern drive, I/O – engine to the rear of the vessel, but enclosed inside the vessel with the drive portion outside of the transom
Inboard – Engine enclosed inside the vessel, mostly located in the center of the vessel but sometimes located near the rear of the vessel (if a V-drive type). Drive (propeller) shaft extends rearward out of the bottom of the vessel through the stuffing box and attaches to the propeller