[Code of Federal Regulations] [Title 40, Volume 18] [Revised as of July 1, 2003] From the U.S. Government Printing Office via GPO Access [CITE: 40CFR91.109] [Page 303] TITLE 40--PROTECTION OF ENVIRONMENT CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PART 91--CONTROL OF EMISSIONS FROM MARINE SPARK-IGNITION ENGINES--Table of Contents Subpart B--Emission Standards and Certification Provisions Sec. 91.109 Requirement of certification--closed crankcase. (a) An engine's crankcase must be closed. (b) For purposes of this section, crankcase means the housing for the crankshaft and other related internal parts.