46 CFR 58.01-35: Duplicate auxiliary machinery for main propulsion
Last reviewed: October 14, 2026
This section covers auxiliary machinery vital to the main propulsion system. Such machinery must be provided in duplicate, with stated exceptions. A note explains when a partial reduction of propulsion capability is acceptable.
Applies toAuxiliary machinery vital to the main propulsion system.
What it says
Auxiliary machinery vital to the main propulsion system must be provided in duplicate.
“Auxiliary machinery vital to the main propulsion system must be provided in duplicate”
Duplicate auxiliary machinery is not required if the system served is provided in independent duplicate.
“unless the system served is provided in independent duplicate”
Duplicate auxiliary machinery is also not required if the system otherwise provides continued or restored propulsion capability after a failure or malfunction of any single auxiliary component.
“or otherwise provides continued or restored propulsion capability in the event of a failure or malfunction of any single auxiliary component”
The note says a partial reduction of normal propulsion capability is acceptable if the reduced capability is not below what the vessel needs to run ahead at 7 knots or half speed, whichever is less, and is adequate to maintain control of the ship.
“Partial reduction of normal propulsion capability as a result of malfunction or failure is acceptable if the reduced capability is not below that necessary for the vessel to run ahead at 7 knots or half speed, whichever is less, and is adequate to maintain control of the ship.”
Common questions
Does auxiliary machinery for main propulsion have to be duplicated?
Yes, auxiliary machinery vital to the main propulsion system must be provided in duplicate, unless an exception in the section applies.
“Auxiliary machinery vital to the main propulsion system must be provided in duplicate”
When is duplicate propulsion auxiliary machinery not required?
It is not required if the system served is provided in independent duplicate. It is also not required if the system otherwise provides continued or restored propulsion capability after any single auxiliary component fails or malfunctions.
“unless the system served is provided in independent duplicate, or otherwise provides continued or restored propulsion capability”
Is a partial loss of propulsion acceptable after a failure?
The note says partial reduction is acceptable if the reduced capability is not below that needed to run ahead at 7 knots or half speed, whichever is less, and still maintains control of the ship.
“if the reduced capability is not below that necessary for the vessel to run ahead at 7 knots or half speed, whichever is less”
The text of 46 CFR 58.01-35
Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR
Main propulsion auxiliary machinery
Auxiliary machinery vital to the main propulsion system must be provided in duplicate unless the system served is provided in independent duplicate, or otherwise provides continued or restored propulsion capability in the event of a failure or malfunction of any single auxiliary component.
Note 1 to § 58.01-30: Partial reduction of normal propulsion capability as a result of malfunction or failure is acceptable if the reduced capability is not below that necessary for the vessel to run ahead at 7 knots or half speed, whichever is less, and is adequate to maintain control of the ship.
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.