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USCG Credential Tonnage Increase Requirements for Mariners Holding Master 25/50 GRT & Mate 25/50/100 GRT

master tonnage increase

The Coast Guard has set out the sea service requirements for Mariners Holding Master 25 or 50 GRT or Mate 25, 50, or 100 GRT increasing tonnage. This is usually called the Increase in Scope. Here we are dealing with increase in tonnage limitation for mariners who, based on their experience acquired after they have been issued Master or Mate licenses with tonnage limitations.

Increase in Scope is defined as a change in horsepower or tonnage limitations, or geographic route restrictions. Whereas Raise of Grade (raise-in-grade) means an increase in the level of authority and responsibility associated with an officer endorsement (For e.g. From Mate to Master).


Vessels are eligible to be documented if they are wholly owned by a citizen of the United States and measure at least five net tons. Net tonnage is a measure of a vessel’s volume and most vessels more than 25 feet in length will measure five net tons or more.

master 25 50 ton increase in scope

Increase in Scope is defined as a change in horsepower or tonnage limitations, or geographic route restrictions

Master/Mate Tonnage Increase General Requirements




  • Must have U.S. Citizenship
  • Must be at least age 19
  • Approved Medical Certificate 

Master 25 or 50 GRT Tonnage Increase Requirements

  • DOES NOT apply to mariners holding master 100 upgrading to master 200 GRT - Examinations are required when raising grade from master 100 GRT to master 200 GRT

Sea Service Requirements

  • If holding Master 25 GRT (service on deck, any position) - 90 days additional service on vessels of 0 - 25 GRT to increase to 50 GRT
  • If holding Master 50 GRT (service on deck, any position) - 90 days additional service on vessels of 0 - 50 GRT to increase to 100GRT
  • Recalculation is done using original requirements for the endorsement, including all service obtained

Mate 25 or 50 or 100 GRT Tonnage Increase Requirements

Sea Service Requirements

  • If holding Mate 25 GRT (service on deck, any position) - 45 days additional service on vessels of 0 - 25 GRT to increase to 50GRT
  • If holding Mate 50 GRT (service on deck, any position) - 45 days additional service on vessels of 0 - 50 GRT to increase to 100GRT
  • If holding Mate 100 GRT (service on deck, any position) - 45 days additional service on vessels of 0 - 100 GRT to increase to 200 GRT
  • Recalculation is done using original requirements for the endorsement, including all service obtained

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Disclaimer: For general information purpose - please check with USCG for the latest requirements and accurate info