The Oberdorfer cooling water pump mounts just like the original gear pump. It is flange mounted to the engine with 2 bolts. Nothing is glued. Unless someone once did a very Mickey Mouse conversion the missing bolts should be obvious. The only other possiblity is that the pump housing itself broke. You should have about an inch of shaft sticking out from the flanged end of the pump.

For a good picture of the pump and it's parts, check the Moyer Marine online catalog. Don sells the complete pump and any parts you may need to fix it.