Merchant Marine Investment Act of 1993

Merchant Marine Investment Act of 1993 - Amends the Merchant Marine Act, 1936 (MMA) to modify the types of vessels eligible to enter into, and the types of vessels qualified to receive payments through, capital construction fund (CCF) agreements.

Restricts CCFs to vessels documented for operation in the foreign or domestic commerce of the United States (currently, for operation in the United States foreign, Great Lakes, or noncontiguous domestic trade) or in the fisheries of the United States.

Amends the MMA and the Internal Revenue Code (IRC) to provide for the income tax treatment of CCF earnings, including regarding capital gains and tax rates. Modifies the ceiling on CCF deposits. Prohibits taking into account amounts included in taxable earnings of the fund for provisions regulating the consistency of the CCF ordinary income account.

Allows: (1) payments that reduce the principal amount of a qualified lease to be considered qualified withdrawals and includes the payments in provisions relating to reductions in basis; and (2) CCF deposits exceeding the ceiling for prior years because of an audit adjustment.

Modifies requirements regarding: (1) the content of CCF capital gains and ordinary income accounts; (2) the tax rate and interest on nonqualified withdrawals; and (3) investment of CCF amounts.

Amends the IRC to require that terms defined in the provisions of the MMA amended by this Act have the same meaning for the provisions of the IRC amended by this Act as the definitional provisions of the MMA that were in effect on the date of the enactment of this Act (currently, on the date of the enactment of the IRC provisions amended by this Act).

Removes provisions providing for the treatment CCFs regarding the alternative minimum taxable income of a corporation.

Classifies vessels (other than fishing vessels) that are eligible vessels under CCF provisions as three-year property for IRC provisions regarding accelerated cost recovery. Sets forth a special rule for determining the amount of depreciation or amortization allowable in connection with adjustments based on adjusted current earnings for provisions relating to adjustments in computing alternative minimum taxable income.