The most important part of a steamer is – of course – the steam engine and the boilers. In early times heated by wood, then by coal and today by diesel, the boilers are producing hot steam, which powers the engine with its enormous pressure. The engine then transforms the steam pressure to paddlewheel-rotation.
The engineer was an important man, because he was the one to control the engine and the only one who knew about the pressure, the boiler possibly could resist without bursting and causing a total desaster. The higher the pressure, the faster the boat. So the engineers often had to go to the limits, because the boat had to go as fast as possible.
Many steamboats (and their passengers) died by boiler explosions. Such explosions also could be dangerous for the cities. As a boat explosion happend at the landing or nearby, often parts of the cities burned down, too.