Section 11.442 - Requirements for master of Great Lakes and inland self-propelled vessels of less than 1,600 GRT(a) The minimum service required to qualify an applicant for an endorsement as master of Great Lakes and inland self-propelled vessels of less than 1,600 GRT is- (1) Three years of total service on vessels. Eighteen months of the required service must have been on vessels of 100 GRT or more. One year of the required service must have been as a master, mate, or equivalent position on vessels of 100 GRT or more while holding a license or MMC endorsement as master, mate, or master of towing vessels; or(2) Six months of service as operator on vessels of 100 GRT or more while holding a license or MMC endorsement as master of towing vessels.