Hi Bob,
Get a mirror and a flashlight and look up into the nipple from the bottom, it may have a hex shaped hole in the inside. If so, you can put an Allen wrench up into the nipple and turn it. If not, then I would look into the parts manual for the thread size, get two nuts of that size, thread them onto the nipple and tighten them against each other with two wrenches and then unscrew the nipple to increase its length enough to comfortably engage the filter when installed. You can put a straightedge across the filter gasket and measure down to the bottom of the female threads in the filter to get an idea of how much exposed thread you should unscrew the nipple.
Another thought, the female threads in the filter head assembly should have been cut so as to leave a lip that would stop the nipple at the correct position. The previous owner may have forced on a filter of the wrong thread and while doing so overtightened the nipple forcing it to break thru the lip in the filter head assembly, something to think about!!
Mad Mackie In CT:laughing::biggrin::smile: