Cowdenbeath scored their first in the 14th minute when Pat Clarke played in Liam Buchanan and the wing-half slotted home from 12-yards.
Ayr missed first half chances to stay in the game with Jerome Vareille and Gavin Friels passing up golden opportunities from close range.
The Blue Brazil made them pay when Clarke slammed home a second goal early after the re-start to put Ayr on the rack.
The home side pushed forward again and skipper Raymond Logan hit the post. In seeking to get back in the gamr United left gaping holes in defence which were soon exploited.
Markus Paatelainen sent Clarke racing through for number three before full-back Mark Baxter hammered home a 25-yard stunner to complete the thrashing.
Ayr fans registered their disgust at ful-time with a chorus of boos but in truth their team was well-beaten.