Merchant Marine Act of 1983

Merchant Marine Act of 1983 - Title I - Amends the Merchant Marine Act, 1936, to allow the Secretary of Transportation to authorize an operator receiving or applying for an operating-differential subsidy to construct or reconstruct its vessels in a foreign shipyard or to acquire them outside the United States. Restricts such authorization to vessels over 5,000 deadweight tons which are suitable for use for national defense or military purposes in time of war or national emergency. Eliminates preconditions for such authorization.

Sets forth criteria of age, period of documentation, and necessity to national defense according to which vessels constructed outside the United States shall be deemed privately owned United States-flag commercial vessels for the purpose of transporting government cargoes.

Revises the definition of "citizen of the United States" to increase the authorized foreign investment in certain corporations, partnerships, or associations engaged in U.S.-flag shipping.

Makes conforming amendments to the Shipping Act, 1916.

Title II - Allows eligible foreign-built vessels to enter into an agreement with the Secretary to establish a capital construction fund.

Amends the Tariff Act of 1930 to repeal provisions requiring a 50 percent ad valorem duty on the costs of vessel repairs made abroad.

Amends the Merchant Marine Act, 1936, to remove the exception for emergencies in the requirement that operators receiving an operating- differential subsidy for repairs make such repairs within the United States or Puerto Rico.