La fan blade bolt threads fine???

I bought a new water pump a year + ago. Painted it nice . Mounted it to the block. Fast forward a year and finally get around to putting the fan on and the coarse thread bolts from the original don't want thread in . I have a fine thread tapper that spins right in . I guess I could get another but its painted . Has anyone else had this happen. Maybe I could run a coarse tapper in and re tap. Suggestions? Thanks