The Robo-Boiler, referred to in-game as the Roboiler, is the second boss of Sonic Spinball for the Sega Mega Drive. As the boss of Mount Mobius' Lava Powerhouse, the Robo-Boiler serves some function in regulating power supply to the Veg-O-Machine. As it stands, all the multiple Roboheads really do is sit there inside a boiler, vomiting lava whenever Sonic hits them.
All 4 of the robotic faces must be destroyed by jumping into their chamber and rattling about; though whenever one gets taken out, the remaining Roboheads will temporarily vanish, leaving Sonic to tumble out of the vessel and have to make his way back up. The two greatest hazards in this boss are:
- The steam jets which guard the lip of the vat; time a jump wrong, and Sonic will get thrown off the ledge and drop back down.
- Falling through the flippers, which will drop him to the extreme bottom of the level; Sonic will hang by a chain for dear life, over a pool of lava, and the player has 10 seconds to swing on the chain with and and jump correctly... or else. The chain will only save Sonic twice; it won't be there the third time he falls down to the bottom.
Hitting the targets on the Robo-Boiler's underside will close the drain plugs, which will redirect Sonic to the steam arena if he falls into the outlanes. Golden Ferrons will periodically appear to get in the way, but they are destroyed in a single hit.
||Destroy Dr. Robotnik's half-baked bosses in the Robo-Boiler Room!
— Sonic Spinball US manual