29 CFR §1915.164

1. (a)Before work is performed on the main engine, reduction gear, or connecting accessories, the employer shall ensure that the following steps are taken:
   1. (1)The jacking gear shall be engaged to prevent the main engine from turning over. A sign shall be posted at the throttle indicating that the jacking gear is engaged. This sign shall not be removed until the jacking gear can be safely disengaged.
   2. (2)If the jacking gear is steam driven, the employer shall ensure that the stop valves to the jacking gear are secured, and then locked or tagged, in accordance with § 1915.89.
   3. (3)If the jacking gear is electrically driven, the circuit controlling the jacking gear shall be de-energized by tripping the circuit breaker, opening the switch, or removing the fuse, whichever is appropriate, and then locked or tagged in accordance with § 1915.89.
2. (b)Before the jacking engine is operated, the following precautions shall be taken:
   1. (1)A check shall be made to ensure that all employees, equipment, and tools are clear of the engine, reduction gear, and its connecting accessories.
   2. (2)A check shall be made to ensure that all employees, equipment and tools are free of the propeller.
3. (c)Before work is started on or in the immediate vicinity of the propeller, a warning sign calling attention to the fact that employees are working in that area shall be hung in a conspicuous location in the engine room. This sign shall not be removed until it is determined that the work is completed and all employees are free of the propeller.
4. (d)Before the main engine is turned over (e.g., when warming up before departure or testing after an overhaul) a check shall be made to ensure that all employees, equipment, and tools are free of the propeller.