Fairly new to me boat with B1x's with about 277 hours on them. Besides changing the drive oil, is there anything that should be done with this many hours?

Torque the gimbal ring nuts, make sure the wear pads that contact the gimbal ring flanges are there, if it's a HP gimbal, check the hinge pin screws/bolts, if STD, take off the senders and check the hinge pins for being tight, check the bellows for any signs of cracking and if the oil comes out clean, don't worry about it

Sorry gotta be stupid and ask where in mechanicsburg? Only asking cause that's where I'm from too, not too many performance boats around here

pressure test outdrive per Merc specs after draining the gear oil - before filling with new gear oil.

Sent you a PM

pull the drive off and have the alignment checked. Change zincs for the correct ones for freshwater if that is where it is being used.