Final answer:
Without specific regulatory context or standards, it's not possible to provide an accurate answer to the maximum horsepower a second-class engineer is allowed to manage for a boiler plant.
Step-by-step explanation:
The question is asking to identify the maximum horsepower a second-class engineer is allowed to be responsible for when making a complete charge of a boiler plant. According to regulations or standards, which can vary by jurisdiction, a second-class engineer may have limitations on the size of the plant they can operate.
However, the specific limitations for second-class engineers are not provided in the materials referenced. Therefore, without specific regulatory context, it is not possible to accurately answer this question.