It is very rare for these pumps to burn out, the more common scenarios are that the drive unit (impeller) is seized to the metal axle that it should spin on freely or the impeller is broken in such a way that the magnet turns without engaging the impeller blades.
You should be able to remove the black rubber ends of the shaft and pull the shaft out of the impeller and magnet, if it is stuck, this is definitely the issue and you will need to seperate them and soak the pieces in 50/50 vinegar and water to dissolve the built up lime.
If the impeller magnet has a loose grey washer of plastic on the bottom, then the magnet has separated from the plastic that drives the impeller. This is cast as one piece on the magnetic core and the bottom will sometimes shear off if fine sand gets in the pump or calcium has built up in the base of the pump. The impellers are available separately, part 1073.087.
If this is not it, the pump has a 2 year warranty covering defects, but not neglect, abuse or modification. If it failed but was otherwise maintained and not modified we would replace it. You would just need to send it in. Marine Depot, Salty Supply and Premium Aquatics stock these pumps, part 1073.008, you can also order one on Tunze.com.
