Squeeze juice from fruit. Grind peels and pulp in food processor. To the mixture of fruit and pulp add 3 cups of water for every cup of fruit, as limes are very strong and not very juicy. Bring these ingredients to a boil in a non-reactive pan; boil until the mixture is tender and reduced by half. For each cup of this mixture, add 3/4 cup sugar. Stir until all the sugar is dissolved and mixture reaches a rolling boil. Reduce heat somewhat, keeping mixture boiling. Stir occasionally. Test after 25 minutes. Ladle into preheated, sterilized jars and cover marmalade with melted paraffin wax to seal.