What year did the engines change Generations
 

From the Mark4 to the Gen V and then the Gen VI?

Jon

I`m pretty sure the mark4 was discontinued in late 1990 then the mark 5 until 1996 when the mark 6 was introduced.

Jon: Theres a very good book
about Gen IV, V amd VI 454
BB motors.
Its A HPBooks-1357 By Mike
Mavrigian.
Really tells what you are asking about.
Mike J.

Merc has Gen V's listed from 1992-1997 and Gen VI's from 1996 on. Looks like 1996-1997 could be either V's or IV's.