Wash the oranges and put in a large pan with the water and lemon juice. Bring to the boil, partly cover and simmer for 21/2 hours, until the oranges are very soft. Remove from the heat and scoop the oranges out into a large bowl. When they are cool enough to handle, cut them in half and scoop the flesh and seeds back into the pan using a dessertspoon. Bring back to the boil and simmer uncovered for 30 mins.
Meanwhile cut the orange peel into strips(either using a sharp knife or knife and fork for a chunkier style). Press the contents of the pan through a sieve into a preserving pan, pressing though as much pulp as possible. Add the peel, sugar and treacle or molasses to the pan. Put a couple of saucers in the freezer.
Bring slowly to the boil, stirring to dissolve the sugar, then raise the heat and boil rapidly until setting point is reached. This should take around 6-10 mins. To test this turn off the heat under the marmalade, take a saucer out of the freezer and spoon on a little blob of marmalade. Leave for a moment, then push the marmalade with your finger. If the surface wrinkles it is ready, if not boil for a few more minutes and test again.
Stir the whiskey into the marmalade, then leave it to cool for 10 mins. Give it a stir to distribute the peel, then spoon into clean warm jars(put them through the dishwasher and leave to dry or wash and drain, then wash well, then warm in the oven for 10 mins) cover and label.