Strawberry Banana Jam

This is really delicious. It's just a little runnier than I like. Not sure how to fix that, but I'm going to work on that next year. if anyone has any ideas, let me know, because this is a recipe worth keeping.

4 3/4 cups crushed strawberries

1 1/2 cups mashed banana

3 tablespoons lemon juice

6 3/4 cups sugar

1 box 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 invert jars for 5 minutes or seal in water bath.