Strawberry Banana Jam

4 3/4 cups crushed strawberries

1 1/2 cups mashed banana

3 tablespoons lemon juice

6 3/4 cups sugar

2 boxes Sure Jell

1/2 teaspoon butter

Mix fruit and lemon juice, stir Sure Jell into fruit; add butter, bring to a rolling boil, stirring constantly. Quickly stir in sugar and remove from heat. Skim off foam, ladle quickly into hot jars cap and seal in water bath.