sheared screws

[gbf03]

The pre owner of my boat had installed fiberglass splash rails and over the years many of the screws corroded out or were sheared off at the head. I am almost at the painting stage in my boat so I removed the splash rails, I was able to remove the majority of the screws but for the ones with no head and barely any shaft sticking out I was unable to. What is the best way to remove them?
Thanks,
George