Looks like the lower unit could be the same. The 1993 uses a different crankshaft and slightly larger diameter pistons than the 1985 motor. The ignition systems are different. The 1985 motor uses breaker points for the ignition system, the 1993 is electronic ignition, no points, which means nothing will interchange.
I don't show any power trim components in the parts manual for a 1985 50HP motor. But then again, I've seen several discrepancies in the parts manuals, so I wouldn't say 100% for sure that power trim didn't come on 1985 50HP motors. Maybe it was added later? I do know that generally speaking, the power trim units for the older motors 1989 and earlier are different from the 1990 and later motors. The physical mounting of the pump is different so it's not like you can take a unit off of an older motor and simply bolt it on to your motor.
Unless you can confirm by looking at and comparing the lower units, and that the power trim pump is the same as yours, It may not be that great of a deal for your needs.