See the Electronic Code of Federal Regulations (e-CFR) for the full text of current regulations that apply to Marine SI engines:

40 CFR part 91 Original exhaust emission standards and compliance program
40 CFR part 1045 Exhaust emission standards for 2010 and later model year engines
40 CFR part 1060 Evaporative emission standards
40 CFR part 1065 Engine-testing regulations for 2010 standards
40 CFR part 1068 General compliance provisions for evap standards and 2010 exhaust standards
Summary of exhaust emission standards and evaporative emission standards
Direct Final Rule — 2010 Technical Amendments : Technical Amendments for Marine Spark-Ignition Engines and Vessels (published September 16, 2010)
Fact Sheet: Technical Amendments for Marine Spark-Ignition Engines and Vessels | PDF Version (2 pp, 495K, EPA-420-F-10-047, September 16, 2010)
Direct Final Rule | PDF Version (7 pp, 78K, published September 16, 2010)
Greenhouse Gas Reporting Rule (published October 30, 2009)
Federal Register Notice
See Greenhouse Gas Reporting for more information.
Final Rule: Control of Emissions from Nonroad Spark-Ignition Engines and Equipment (published October 8, 2008)
Fact Sheet: EPA Finalizes Emission Standards for New Nonroad Spark-Ignition Engines, Equipment, and Vessels | PDF Version (5 pp, 205K, September 2008, EPA420-F-08-013)
Final Rule (PDF) (348 pages, 5.4MB)
Final Regulatory Impact Analysis (PDF) (808 pp, 8.5MB, September 2008, EPA420-R-08-014) Instead of downloading the entire document, you can access individual chapters.
Summary and Analysis of Comments (PDF) (480 pp, 3.1MB, September 2008, EPA420-R-08-016) Instead of downloading the entire document, you can access individual chapters.
See the May 18, 2007 Proposal and the August 14, 2002 Proposal for the proposed rules and the related fact sheets and technical support documents.
Final 2005 Technical Amendments – Procedures for Testing Highway and Nonroad Engines and Omnibus Technical Amendments (published July 13, 2005)
Fact Sheet: Regulatory Announcement: Changed Test Procedures for Nonroad Engines and Heavy-Duty Highway Engines | PDF Version (4 pp, 134K, EPA420-F-05-036, July 2005)
Federal Register Notice
Technical Support Document and Summary & Analysis of Comments (PDF) (115 pp, 1663K, EPA420-R-05-008, June 2005)
See Proposed Technical Amendments for the proposed rule, fact sheet, and technical support documents (published September 10, 2004)
Final 2002 Technical Amendments to 40 CFR part 91 (published November 8, 2002)
Federal Register Notice | PDF Version (207 pp, 1.1MB)
Other related documents regarding the final rule are available at: www.epa.gov/otaq/regs/nonroad/2002/cleanrec-final.htm
Proposal for Cleaner Recreational Vehicles with Proposed Technical Amendments to 40 CFR Part 91.
Final 2000 Technical Amendments (published April 25, 2000)
Federal Register Notice
Proposed Rule: Federal Register Notice | PDF Version (8 pp, 63K, February 1999)
Final 1997 Amendment to 40 CFR part 91 (published April 2, 1997)
Federal Register Notice
Final Rule for New Spark-Ignition Marine Engines (published October 4, 1996)
Federal Register Notice | PDF Version (83 pp, 890K)
Fact Sheet: Emission Standards for New Gasoline Marine Engines | PDF Version (4 pp, 13K, EPA420-F-96-012, August 1996)
Regulatory Impact Analysis (PDF) (85 pp, 414K, June 1966)
Nonroad Engine and Vehicle Emission Study Report (Publication no. EPA-21A-2001 or EPA460/3-91-002, November 1991)
This “nonroad study” quantifies the contribution of nonroad sources to air pollution, including volatile organic compounds (VOCs), oxides of nitrogen (NOx), carbon monoxide (CO), and particulate matter (PM). The study covers 10 equipment categories, including: lawn and garden equipment, farm and construction equipment, recreational vehicles, marine vessels, and airport service equipment.