Which modification is not allowed for MRCs by shipboard personnel?

The correct answer relates to the strict adherence to the Standardized Instruction System and the operational procedures established for Maintenance Requirement Cards (MRCs). MRCs are critical documents that outline the specific maintenance tasks, tools, and procedures required for different systems and components aboard a vessel.

When it comes to using test equipment or certified tools, there are stringent regulations in place to maintain safety and reliability. While it may seem logical that modern or updated tools could be of value, the requirement to meet or exceed the SCAT (Standardization of Compressed Air Tools) code ensures that only tools that have been specifically approved for the intended use are permissible. Using tools or equipment that do not hold a valid certification within the specified parameters can lead to safety risks and operational inefficiencies, making this modification unacceptable.

In contrast, the other options highlight permissible actions that allow for some level of flexibility while still maintaining the integrity of the MRCs. Substituting common hand tools and basic housekeeping items, using approved parts or materials from the supply system, and line-out procedures that are not applicable show how shipboard personnel can adapt to situations while adhering to established guidelines. Collectively, these allowances are designed to ensure that maintenance can proceed effectively without compromising the overall standard of care