I am so tempted (but would never) to say; "that is why they invented warranties", but until you have checked all the other possibilities; "it just wouldn't be prudent".
What is the voltage at the the starter, and when cranking? neg lead at the battery then at the frame.
Check for a voltage drop somewhere else (like on the ground between the frame, battery neg, and the motor)? maybe battery cable ends? if you pull the starter what happens? is the nose cone OK?
does this unit have a key switch that can return to the start position without going to off?

Starter is Brand New

replace the starter. brushes are worn out