I found an error in our Nomemade cookbook and I wanted to post the correction here.
Use 1 1/2 cups of water NOT 1/2 cup.
The full corrected recipe is listed below...
3 1/2 cups mountain cranberrries (aka lingonberries)
1 1/2 cups water
2 cups mashed bananas
7 cups sugar
3 oz. Certo liquid pectin
Simmer the cranberries and water together, in a large saucepan, for 7 minutes. Add the bananas and sugar, and bring the mixture to a boil. Add the Certo, and bring it back to a boil for 1 minute. Remove the jam from the heat, and pour into clean jars for sealing.