I can't find anything on that Part Number, But I would Guess it is an "N" Mosfet, rated at 70 Volts and 80 Amps.
Seems Strange such a High power MOSFET and No Heat Sink?
Probably a STP75NF75 would be a good replacement.
The Y5163 04G, is Just the manufactured Date Code.
I could send you 2 of...