1 Labor to replace a starter motor on a vehicle with relatively easy access typically takes about 30 minutes to two hours at $50-$120 an hour (ranging from an independent mechanic to a dealership).2  This brings typical total costs (parts and labor) to install a starter motor on an easy-access vehicle to $150-$600. The total cost may include a labor charge of an hour or so (at $50-$120 an hour) for diagnostic testing to determine whether the starter motor should be replaced. 2  Popular Mechanics explains how to diagnose a bad starter motor and AutoZone provides a video explanation of the diagnostic process.