Allows hour monitoring for even the smallest gasoline motors. Great for 2 or 4 stroke. No power or ground required. Water and shock proof. Automatically turns on and off with the engine. Displays up to 9999 hours. 10 year internal battery lifetime. Replaces: Yamaha ENG-METER-2C-01. Features:. No power or ground required. Water and shock proof. Automatically turns on and off with the engine. Displays up to 9999 hours. 10 year internal battery lifetime