What feature allows the house batteries to power the engine in case of battery failure?

The correct answer highlights an essential feature found in many rescue boats known as the Emergency Boost Feature. This feature enables the house batteries to provide power to the engine if there is a failure in the primary battery system. This capability is crucial in emergency situations where immediate propulsion is necessary to ensure safety and functionality.

The Emergency Boost Feature typically involves a system that connects the house batteries to the engine's starting circuit, allowing the boat to be propelled even when the main starting battery cannot perform its function. This redundancy in power supply is vital for rescue operations, where reliability can mean the difference between effective response and complications.

In contrast, the other options do not serve the same specific purpose. A Backup Charger may provide additional charging capacity but does not explicitly facilitate powering the engine directly from the house batteries. A Manual Override can allow operators to control certain systems manually but does not guarantee that power can be rerouted to the engine during a failure. Similarly, a Power Transfer Switch may direct power from one source to another but does not inherently include the feature necessary for an automatic emergency boost from house batteries to the engine, which is what is being addressed in this context.