40 CFR 91.203 - General provisions.
(b) A marine SI engine family must use the averaging provisions and may use the banking and trading provisions for hydrocarbon plus oxides of nitrogen emissions if it is subject to regulation under subpart B of this part with certain exceptions specified in paragraph (c) of this section.
(1) Which are exported, or
(d) A manufacturer may certify marine SI engine families at Family Emission Limits (FELs) above or below the applicable emission standard, provided the summation of the manufacturer's projected balance of all credit transactions in a given model year is greater than or equal to zero, as determined under § 91.207.
(1) A manufacturer of an engine family with an FEL exceeding the applicable emission standard must obtain positive emission credits sufficient to address the associated credit shortfall via averaging, banking, or trading.
(2) An engine family with an FEL below the applicable emission standard may generate positive emission credits for averaging, banking, or trading, or a combination thereof. Emission credits may not be used to offset an engine family's emissions that exceed its applicable FEL. Credits may not be used to remedy nonconformity determined by a production line testing, a Selective Enforcement Audit (SEA) or by recall (in-use) testing. However, in the case of a manufacturer production line testing or SEA failure, credits may be used to allow subsequent production of engines for the family in question if the manufacturer elects to recertify to a higher FEL. In the case of production line testing a manufacturer may revise the FEL based upon production line testing results obtained under subpart F and upon Administrator approval pursuant to § 91.122(d).
(e) Credits generated in a given model year may be used in the following three model years. Credits not used by the end of the third model year after being generated are forfeited. Credits generated in one model year may not be used for prior model years, unless allowed under § 91.207.
(f) Manufacturers must demonstrate compliance under the averaging, banking, and trading provisions for a particular model year by 270 days after the model year. An engine family generating negative credits for which the manufacturer does not obtain or generate an adequate number of positive credits from the same or previous model years will violate the conditions of the certificate of conformity. The certificate of conformity may be voided ab initio pursuant to § 91.123 for this engine family.