409 belt alignment issue

[HydroWAL]

Long story short. Annual service was done. About 7 hours after the idler pulley and belt went. I have replaced them but the belt is riding up on the shoulder out the alternator pulley. I have aligned the belt several times but as soon as the motor turns over it jumps back up on the shoulder. All the pulleys are tight, the belt is aligned everywhere else. Could something have gotten out of line when the impeller was changed. Any help or suggestions would be appreciated.
Thanks Bill

[Infinity]

Was it staying aligned right after idler pulley was replaced and didnt start getting on shoulder till after an impeller change? Since impeller is only held on with those 3 screws, if not properly installed you would think the impeller housing would be leaking water like crazy and not wanting to prime. Its possible the alterator pulley or one of the others is out of whack and is causing the issue, if you remove the belt by hand and turn all the pulleys, do any of them not feel right...I dont think the alternator itself is adjustable, but perhaps the bearings on that pulley are worn out?

[scottb7]

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https://www.ebay.com/itm/Gates-Racin...AAAOSw5SlcsWoH

Or maybe even figure out how to secure small laser pointer with similar method for "free99"...

[HydroWAL]

Thanks for the replies. After looking at it again this morning, the only thing I can find out of the ordinary is a little slop in the tensioner pulley. Maybe it is throwing the belt at the idler pulley at an angle that is slightly off. I will try replacing it and see how it goes. Thanks again for your help.

[HydroWAL]

Changed the tensioner pulley, the belt is still riding up on the alternator pulley. I guess I'll change out the tensioner assembly next.