I just purchased a 93 F336 with 525's.
I don't much about supercharged motors.
The boat was a bank repo, so I don't know anything
as far as service history goes. The boat has 250 hr's.
I's there anything special I need to do other then oil,
gear, water separators (normal maintenance).
I's there oil or gear fluid in the superchargers that
need annual changing.
Any tips or advice is greatly appreciated.

Yes there is, both front and rear of the blower have lube. The front does have a little dip stick which allows you to check the level, the rear only has the plug. They are somewhat a pain to change, no drain holes. When I had mine I made up a small plastic hose to adapt to my oil changer to be able to suck it out. Definitely change it, check it often, some of the earlier styles had a tendency to push lube past the seals, not a real big deal but needs to be checked. The blowers can be upgraded to the newer style seals if you need that done.

These are great engines and will go a long time if maintained properly. With 250 hrs it would not hurt to at least take a look at the valve train. Being a flat tappet hydraulic it is fairly low maintenance, but worth a look see.