The allowances and restrictions for an OSV to transfer fuel is determined by the transferring OSV’s tonnage.
Under current regulations and the U.S. Code, if the transferring vessel is as an OSV, < 500 GRT/6000 GT ITC, then it may transfer fuel to other vessels and offshore drilling or production facilities that are in support of exploration, exploitation, or production of offshore minerals or energy resources (including wind). However, OSVs, > 500 GRT/6000 GT ITC, may only transfer fuel from fuel supply tanks to offshore drilling or production facilities in the oil industry and not to any other vessels.
Please see the following flowchart. A pdf of the flowchart is also available here.

Read on for further information/insight related to these OSV categories...
The answers are found in 46 U.S. Code (U.S.C.) Chapters 21 and 37. Also, for OSVs, > 500 GRT/6000 GT ITC, we must refer to 46 CFR 125.115 for addition information.
46 U.S.C. § 2101 "General Definitions", defines an "Offshore Supply Vessel" as "…a motor vessel that regularly carries goods, supplies, individuals in addition to the crew, or equipment in support of exploration, exploitation, or production of offshore minerals or energy resources."
Paragraph (b)(1) under the "Tank Vessel Definition Clarification" found in 46 U.S.C. § 2101, states that an offshore supply vessel of less than 500 gross tons (6000 GT ITC1) as measured under section 14502, or alternate tonnage measured under section 14302 of such title as prescribed by the Secretary under section 14104 of such title are deemed not to be a tank vessel for the purpose of any law.
OSVs < 500 GRT/6000 GT ITC
The "Tank Vessel Definition Clarification" found in 46 U.S.C. § 2101 means the "Carriage of Liquid Bulk Dangerous Cargo" rules of 46 U.S.C. § Chapter 37 do not apply to an OSV < 500 GRT/6000 GT ITC. Therefore, an OSV < 500 GT/6000 GT ITC, is allowed to conduct fuel transfer to other vessels only in support of exploration, exploitation, or production of offshore minerals or energy resources (including wind).
OSVs > 500 GRT/6000 GT ITC
OSVs, > 500 GRT/6000 GT ITC, are not exempted in the “Tank Vessel Definition Clarification” found in 46 U.S.C. § 2101 and the "Carriage of Liquid Bulk Dangerous Cargo" rules of 46 U.S.C. § Chapter 37 do apply.
However, 46 U.S.C. § 3702(b) exempts OSVs from the requirements of 46 U.S.C. § Chapter 37 only if they comply with the following paragraph:
(b) This chapter does not apply to a documented vessel that would be subject to this chapter only because of the transfer of fuel from the fuel supply tanks of the vessel to offshore drilling or production facilities in the oil industry if the vessel is—
(1) not a tanker; and
(2) in the service of oil exploitation.
Amplifying information regarding transfer of fuel on OSVs, > 500 GRT/6000 GT ITC, is found in 46 CFR 125.115 which states:
(b) Transfer of excess fuel oil from the fuel supply tanks of an OSV of at least 6,000 GT ITC (500 GRT if GT ITC is not assigned) to an offshore drilling or production facility will not cause Subchapter D of this chapter to apply to the OSV, provided that the vessel is—
(1) Not a tankship as defined in 46 CFR 30.10–67; and
(2) In the service of oil exploitation.
Utilizing the current regulatory exemptions of 46 U.S.C. § 3702(b) and 46 CFR 125.115, OSVs > 500 GRT/6000 GT ITC, are allowed to transfer fuel from the fuel supply tanks only to offshore drilling or production facilities in the oil industry.
All other type of fuel oil transfers would invoke the requirements of "Carriage of Liquid Bulk Dangerous Cargo" requirements of 46 U.S.C. § Chapter 37 and the "Tank Vessels" requirements of 46 CFR Subchapter D.
1 Section 5209 of Pub.L. 102-587, as amended, refers to the specific U.S.C. tonnage measurement section under which the OSV is measured. For clarity the tonnage terms "GRT" for measurement under 46 U.S.C. § 14502 and "GT ITC" for measurement under 46 U.S.C. § 14302 are used in the answers of this FAQ. On December 18, 1996, the Coast Guard amended its regulatory definition of OSV in 46 CFR 125.160, establishing 6000 GT ITC as the alternate maximum tonnage for OSVs (61 FR 66613).
The answers to this FAQ are not all inclusive as it relates to fuel oil transfers. This FAQ does not address pollution prevention, notification requirements, transfer procedures, quantity of fuel, personnel or other operational requirements for the transfers of fuel or hazardous cargoes.
Published 11Jun2019; flowchart added 03Mar2023 and updated 04Aug2023.