Sailing short

How dos it work? If the COI has a Chief and a First engineer listed can they sail short for a couple days if one has to get off for a medical? I know that CG has granted exceptions for equipment, but I am curious about manning.

You can sail short in every position except master. That said, you must have enough crew to cover the voyage, the shortage of crew must have been unintentional, and the master must sign off on it. check cfr 33 or 46