Bring all ingredients to a full rolling boil over medium heat in a Dutch oven, stirring occasionally, until sugar is dissolved and syrup thickens. Reduce heat, and simmer, stirring occasionally, 15 to 20 minutes. Remove from heat; skim off any foam.
Pour hot marmalade immediately into hot, sterilized jars, filling to 1/4 inch from top. Remove air bubbles; wipe jar rims. Cover at once with metal lids, and screw on bands.
Process in boiling-water bath 10 minutes.