When I set the trim to a certain point I must keep adjusting the trim up to maintain the desired setting. I rebuilt both trim cylinders with no change . If I leave the drive up when Im done using the boat the following morning the drive will drop down completely. Are there check valves in the trim pump that can be cleaned or replaced?

What drive and pump might we be talking about?

That would probably help, Bravo drive, not sure what pump, its the original from when the boat was built in 2000.