In addition, what code applies here? Is this a boat
and you need to meet ABYC or your US based home/business where NEC might apply? Is this a continuous service
or intermittent? What voltage drop does the application allow? What is the ambient temperature range? Do you need low smoke cable per insurance
or code requirements?
Personally, I would not use AWG-4 copper for an 80A circuit. But it might be ok depending on several other factors that are unkniwn.