Modern engines can control the air-fuel ratio much more precisely. Earlier boiler operation depended more heavily on the crew judging combustion by eye. Periscopes from the Iowa-class boiler rooms to views of the funnels illustrate that practice. Better control connects the operator's task to the earlier discussion of cleaner combustion and reduced deposits.
Notable Point · 22:22-23:06
Boiler crews once judged combustion by watching the funnels
The Iowa-class funnel-viewing periscopes illustrate how boiler crews monitored combustion before modern controls.