(a) OSVs of less than 6,000 GT ITC (500 GRT if GT ITC is not assigned). (1) Exceptas provided in paragraph (a)(2) of this section, each internal-combustion engine installed on an OSV of less than 6,000 GT ITC (500 GRT if GT ITC is not assigned), whether for main propulsion or for auxiliaries, must be driven by a fuel having a flashpoint of not lower than 43 °C (110 °F) as determined by ASTM D 93 (incorporated by reference, see § 125.180).