An automatic vibrator assembly includes a single vibrator mechanism or first and second vibrator mechanisms connected to first and second switch assemblies that are all housed with a case that attaches between a concrete finishing tool float and adaptor using industry standard bolt layouts. The vibrator mechanisms propel the float when the switch assemblies recognize a predetermined amount of forward and backward float tilt. Where the assembly uses two vibrator mechanisms or a single bidirectional vibrator assembly, the vibrator mechanisms can propel the float in different directions depending on the direction of tilt. Additional features include a variable speed controller, master switch for operating in automatic or manual mode, and docks that accommodate one or two removable batteries.