Rinse the muscadine grapes thoroughly under cold water and drain well.
In a large stock pot, combine the grapes and water over medium heat.
Bring the mixture to a boil and let it simmer for 20-25 minutes until the fruit softens.
Use a masher to crush the grapes, then strain the juice through a cheesecloth-lined colander into a clean pot.
Combine the strained juice with lemon juice and sugar, and bring it to a rolling boil.
Add pectin, return to a boil, and maintain it for 1-2 minutes until the jelly reaches the desired consistency.