What should be done if a boat's bilge pump is not functioning?

If a boat's bilge pump is not functioning, operating it manually until it can be repaired is an effective and responsible action. The bilge pump is a crucial device that helps to remove unwanted water from the bilge area, preventing potential flooding and maintaining the boat's stability and safety. By manually operating the bilge pump, the immediate risk of water accumulation can be mitigated, ensuring that the boat remains safe to operate until the pump can be properly inspected and repaired.

The other options suggest actions that fail to address the immediate safety needs of the boat. Replacing the pump without inspection could lead to unnecessary costs and may not resolve the underlying issue if it's not simply a malfunction. Waiting for a professional can leave the boat vulnerable to flooding in the meantime, which is particularly risky if the boat is in use. Ignoring the issue, especially if water is not visibly accumulating at the moment, is dangerous; water can still accumulate unexpectedly, leading to potential emergencies. Therefore, manually operating the pump is the most prudent and proactive approach to ensure safety.