2007 SV-211 PCM 330 raw water pump pulley cracked. Underlying cause?

[jhoffy22]

Had some issues this weekend with my boat. Noticed a chirping sound at idle that got progressively worse as RPMs increased. The chirping sound quickly turned to a "ratchet" noise. I did some examination and found that the raw water pump pulley had cracked. What could have caused this? Bad raw water pump bearings? Or could it be something else.

Thanks in advance!