I have a 200 fitch its 5 years old now (2000), I have had the boat (with engine) for 1 year. From the service records, nothing has been a problem, as has been looked after and serviced properly AND the proper Evinrude oil.
It has been a very good engine and goes very well.
Some people i know have had to replace the rams, but thats down to people washing the salt off.
I think the earlier ones there were modifications to help with combustion, however mine (2000 model) and newer dont need/have these
I can only speak for mine but its a good engine, i intend to keep it until its knackered (worn out)