If memory serves me correctly, the big problem with those fuel pumps are the check valves which are staked in place by small keepers to hold them in the body of the pump. There are only 3 gaskets and the diaphragm cups are held in place by a small bolt, one cup on each side of the diaphragm. The fuel pump is driven off of the camshaft and is mounted on the cylinder head. If the spring loaded rod that activates the diaphragm comes loose, it is held in place by a pin. Again, that is if my memory is correct. OMC/BRP had some issues with the fuel pumps back in or around 2006 or so. The issue was poor vendor parts and the pumps were back ordered for a long time. I hope this helps.
Regards,
Rick