Many digital cameras go into "E-E" when you push analog video into them. They will repeat the incoming video and audio at the FireWire digital output.
Plug the FireWire into the Mac and launch FCP Log and Capture as an "Uncontrolled Device". Play the Hi8 deck and the show should transfer to the Mac.
If that *doesn't* work. Make a DV tape and transfer that as a FireWire Controlled Device.
Koz