Wash and stem cherries. In a large pot, add cherries and ~3? cups water ? just enough to barely cover.
Simmer (do not boil, to preserve flavor) about 20 min until cherries are soft and skins split, mash occasionally.
Strain through a fine sieve or cheesecloth; do not press if you want clear jelly. Measure 3? cups strained cherry juice.
In a pot, mix juice with one packet pectin; bring to a full rolling boil. Stir in 4? cups sugar.
return to boil and boil hard 1 minute, stirring. Remove from heat, skim foam. Ladle hot jelly into sterilized jars leaving 1/4? headspace. Cap and process in boiling water bath 5 min.
. Cool to set.