((a)) On request of the mortgagee and before executing a preferred mortgage, the mortgagor shall disclose in writing to the mortgagee the existence of any obligation known to the mortgagor on the vessel to be mortgaged.

((b)) After executing a preferred mortgage and before the mortgagee has had a reasonable time to file the mortgage, the mortgagor may not incur, without the consent of the mortgagee, any contractual obligation establishing a lien on the vessel except a lien for—

((1)) wages of a stevedore when employed directly by a person listed in ;

((2)) wages for the crew of the vessel;

((3)) general average; or

((4)) salvage, including contract salvage.

((c)) On conviction of a mortgagor under section 31330(a)(1)(A) or (B) of this title for violating this section, the mortgage indebtedness, at the option of the mortgagee, is payable immediately.