Fan belt problem

Well my fan/alt belt keeps flipping over and i can figure out why . Ive checked all 3 pulleys line up the water pump pulley seems to wobble a bit not sure why all the bolts are tight and the pulley isnt damaged or doesnt seem to be . .

I finally bougth the thinest belt i could find for a lawnmower and it hasnt fliped over yet . The alt and water pump pully are the same width groove but the crank pulley grove is a bit thinner is this the problem .

Jason

Jason, have you laid a straightedge on the face of the pulleys or are you just sighting by eye? Get a good, straight yardstick from the hardware and check the pulley alignment again.

also see if theres any shaft wobble on your water pump.... could be early signs of it going out...