Section 25.40-1 - Tanks and engine spaces(a) All motorboats or motor vessels, except open boats and as provided in paragraphs (d) and (e) of this section, the construction or decking over of which is commenced after April 25, 1940, and which use fuel having a flashpoint of 110 °F., or less, shall have at least two ventilator ducts, fitted with cowls or their equivalent, for the efficient removal of explosive or flammable gases from the bilges of every engine and fuel tank compartment. There shall be at least one exhaust duct installed so as to extend from the open atmosphere to the lower portion of the bilge and at least one intake duct installed so as to extend to a point at least midway to the bilge or at least below the level of the carburetor air intake. The cowls shall be located and trimmed for maximum effectiveness and in such a manner so as to prevent displaced fumes from being recirculated.(b) As used in this section, the term open boats means those motorboats or motor vessels with all engine and fuel tank compartments, and other spaces to which explosive or flammable gases and vapors from these compartments may flow, open to the atmosphere and so arranged as to prevent the entrapment of such gases and vapors within the vessel.(c) Boats built after July 31, 1980, which are manufactured or used primarily for noncommercial use; which are leased, rented, or chartered to another for the latter's noncommercial use; which are engaged in the carriage of six or fewer passengers; or which are in compliance with the requirements of 33 CFR part 183 are exempted from these requirements.(d) Boats built after July 31, 1978, which are manufactured or used primarily for noncommercial use; which are rented, leased, or chartered to another for the latter's noncommercial use; or which engage in conveying six or fewer passengers are exempted from the requirements of paragraph (a) for fuel tank compartments that: (1) Contain a permanently installed fuel tank if each electrical component is ignition protected in accordance with 33 CFR 183.410(a) ; and(2) Contain fuel tanks that vent to the outside of the boat.CGFR 65-50, 30 FR 16653, Dec. 30, 1965, as amended by CGD 76-082A, 44 FR 73047, Dec. 17, 1979; CGD 76-082A, 45 FR 7551, Feb. 4, 1980; CGD 95-012, 60 FR 48048, Sept. 18, 1995; CGD 95-028, 62 FR 51196, Sept. 30, 1997