Pas I have been learning a fair amount while fielding questions on this site. Best I can tell it wasn't until 1998 when mercruiser started using the newer small block V8s that required electic fuel pumps and had provisions for knock sensors and alike. There is also difference between carb and EFI set ups which merc still offers both today.
I believe the 4.3 V6 started changing over earlier as I had a 1992 with an electric fuel pump but not other modern sensors. Also haven't looked at the big blocks enough except that beyond the 7.4 the 8.1, 8.2, and so forth were all high tech.
1997 2400 SCR
5.7 Vortec / Bravo 2