Use a text editor such as notepad to edit the "playconsum.txt" file in the game's "\data\econ" folder. Set all values to zeros so the entries appear as:
Sup Weight(lbs) Per person
Food 0
Fruit 0
Pork 0
Rum 0
This allows you to sail as long as needed as long as at least one ton of those supplies are present. Note: The "Fruit" and "Livestock" commodities will still be used by the crew.
Extra money
Use a text editor such as notepad to edit the "missionbrief.txt and "missioncompleted1.txt" files in the "/data/missions//" folder. In the "missionbrief.txt" file, look for the amount of pesos and increase it to the number desired. In the "missioncompleted1.txt" file, look for the amount of pesos and set the same number. Play the mission and get your reward.