[MastUndSchotbruch]

As far as I know Universal stopped manufacturing the Atomic 4 in 84. It's entirely possible catalina had a skid of Atomic 4s sitting around, but by 89 who would have wanted one?

Don't diss the mighty Atomic-4! There is much to say for it. Simple, non-electronic, quiet, economical, no diesel smell, no diesel bugs, ...
Yes, it uses gas which spawned the 'Atomic bomb' myth. I read somewhere that not a single boat ever exploded due to a fault on the motor. Yes, there have been accidents but that was always due to problems with the tank or fuel lines. (source: internet, so it must be true )

Seriously, I have an Atomic 4 and I have no complaints whatsoever. There is also fantastic support for it, mainly through Moyer Marine and its forums.