Weed-trimmer outboard motor attachment has a lower shaft housing with a proximal coupling to correspondingly mate and engage a distal mid-shaft coupling of an upper part of a motorized weed-trimming device having a motor and a shaft that rotate a number of rotations per minute when operating; a distal termination thereto, which includes a propeller; and a rotation speed reduction unit to reduce a number of rotations of the propeller in relation to the number of rotations of the motor of the motorized weed-trimming device. The attachment can be assembled with the weed-trimming device to provide an outboard motor. A mount for mounting the weed-trimmer outboard motor to a boat can be provided as well.