Bummer Von, I would suggest a temp fix asap of a steel jack pole to support the load of the porch ceiling, which may be rentable from your local rent-all. Then rebuild with pressure treated lumber. Looks like dry rot, can't see how moisture could access that beam unless if what I am seeing are built in/fixed gutters? If so h2o may find it's way back if your roof drainage system is faulty around that porch area, thus the h2o flows inside of the porch ceiling then naturally down the beam which may be another reason for the rot. Good Luck, Eric