In large saucepan, combine corn, onion, potatoes, water and bouillon. Bring to a boil. Reduce heat to low; cover and simmer for 10 minutes or until potatoes are tender, stirring occasionally.
Stir in 1 1/2 cups of the milk and butter. In a small bowl, combine remaining 1/4 cup milk and the flour; beat with wire whisk until smooth. Add flour mixture to chowder; cook and stir until bubbly and thickened.