Wiring diagram is included – use the red and black wires for full speed, or add a three-pole switch for speed control. Prop shaft diameter is 3/8. The motor is reversible (swap the red and black wires). The item “Mercury / MotorGuide variable speed 12V electric outboard motor lower unit only” is in sale since Wednesday, May 15, 2019. This item is in the category “eBay Motors\Parts & Accessories\Boat Parts\Outboard Engines & Components\Lower Unit Components”. The seller is “weartronics-usa” and is located in Hayward, California. This item can be shipped to United States.