throwing belts

has anyone had any problems with the 8 inch pulley alignment? i have been throwing belts lately,but i cant see any problem with the alignment by looking at it, when its running and reving it up .only thing i can think of is i did overrev it and maybe that caused it to come off...boost gauge says 10 lbs ,doesnt make much sense because it starts to come off on the crank pulley on the outside lip.

Is this a Single Belt unit or the Newer Dual belt.

two belt

it seems that the water pump pulley is to fault when i over-reved it the belt was too close to the pulley and it nudged it just slightly enough to hang over the edge of the crank pulley and from there it just worked its way off