Single stage fuel pump issue

[badly bent or broke]

Last fall my '97 75 HP Force would not idle properly and I rebuilt fuel pump. It ran great the next few times out but the same problem came back the last couple of times out. So I figured I messed something up and recently rebuilt it again. Attached are a couple of pictures of a gasket that came out of the pump. Hopefully you can see how the gasket is has lost its shape and is torn. Undoubtedly this allows fuel to leak from one chamber to the other which I suspect is causing my problem. My questions is what would be blowing this gasket and what should I do to correct the problem?