2 cups fresh cumquats
Sugar

Cut fruit finely and remove seeds.   For each cup of fruit add 2 cups of water. Bring the water and fruit to boil and simmer until the skin is very soft.  For every cup of  cooked fruit and water add 1 cup of sugar.    Bring to boil and rapidly cook until  jells.  Bottle hot in sterilized bottles and seal.  Cook in batches of 4 cups fruit/liquid to 4 cups sugar  at a time instead of  making all the marmalade at  once.   Repeat with other batches. 

I find that this usually only takes about 20 minutes to cook  and produces a light marmalade whereas cooking it all at once  does not allow the liquid to evaporate as quickly and can produce darker marmalade.