Railcraft Version: 7.3.0.11
Forge Version: 9.10.0.819
Mods: Forge, Railcraft, Buildcraft, IC2
Issue: I have a full size steam boiler running at max capacity in my test world, while testing I have found that if you are flying above the boiler's highest block, you can not open the GUI (For Example: I have a boiler where the top block is at Y:65, if I fly in the air above Y:65 and click the boiler it shows the right click motion but the GUI doesn't open)

There is a limit to the distance you can be from the source block when opening a gui, in the case of the boilers, the source is the master block in the bottom row.

Ok thanks