Our 1988 Catalina 30 (Universal M25-XP motor and Hurth trans. w/ 1 inch prop shaft) uses 3/16" packing. We like that PTFE impregnated packing, but most any kind will work. Many folks like dripless, but we don't have any problem with the traditional few-drips-per-minute packing. Replacing it is easy once you've become familiar with doing it. We renew our packing when we haul the boat for it's bottom paint. We're also careful to adjust it as necessary once the boat is launched. After a few small adjustments, the packing in the gland will "settle in" and need very little attention until the next time we renew it.