Juice the fruits into a large bowl lined with cheesecloth.
Remove the pulp and flesh from the peels and place into the cheesecloth. Wrap the cheesecloth into a little satchel and gently squeeze the juice from the satchel. Pour the juice from the bowl into a large stockpot.
Add 13 cups of water to the juice and begin heating over medium high heat.
Slice the lemon and orange peels very thinly and add to the stockpot.
Place the satchel of fruit pulp into the stockpot.
Gently boil the mixture for 1½ hours or until the liquid is reduced by half.
Remove the pulp satchel to a clean bowl and allow to cool. Once cool, gently squeeze to release any additional juice. Discard the pulp.
Fill the water bath canner and bring to a boil.
Wash the jars, lids and bands in hot soapy water.
Return the liquid and peels to high heat and bring to a hard boil.
Add the sugar and stir frequently.
Allow the marmalade to boil hard for at least 15 minutes. Gel stage will happen at 220℉. Monitor the temperature until this temperature is reached.
Ladle the hot marmalade into the clean jars, leaving 1/4 inch headspace. Run the bubble popper through the jars to release any trapped air and adjust headspace if needed.
Wipe the rims of the jars with a clean towel and place the lids and bands. Tighten the bands fingertip tight.
Place the jars into the boiling water bath, cover, and process for 10 minutes. (adjust for altitude if necessary)
Remove the jars to a towel lined cutting board and allow to rest for 12 hours before labeling, dating, and storing.