This is something different to do with you cumquats and well worth the effort.
I got this recipe from a Cumquat Nursery.
Yield will depend on size of jars used.I have not included 24 hours standing time in the prep times.
Wash cumquats well. Pull cumquats apart and remove the pips the chop the cumquat up finely. Place the Put the fruit in a bowl. Add 1.25 litres water, cover with plastic wrap and leave overnight.
Put two saucer plates in the freezer (you will see why later) Place the cumquats in a large saucepan with the lemon juice. Bring slowly to the boil, then reduce the heat and simmer, covered, for 30 minutes, or until the fruit is tender.
Add the sugar. Stir over low heat, without boiling, for 5 minutes, or until all the sugar has dissolved. Return the mixture to the boil and boil rapidly, stirring frequently, for 20 minutes. Skim any scum from the surface during cooking with a skimmer or slotted spoon. When the marmalade falls from a tilted wooden spoon in thick sheets without dripping, start testing for setting point.
Remove the saucepan from the heat, place a little marmalade onto one of the cold plates and place in the freezer for 30 seconds. A skin will form on the surface and the marmalade will wrinkle when pushed with your finger when setting point is reached. Remove any scum from the surface.
Spoon immediately into clean, warm jars. Seal jars and turn upside down for 2 minutes, then invert and leave to cool. Label and date. Store in a cool, dark place for 6-12 months. After opening, store in the refrigerator for up to 6 weeks.