Powerhead Base Gasket for Johnson Evinrude High-quality marine engine spare parts. Reference to Johnson / Evinrude : 0315852 0315018 0326468 315852 315018 326468 Applications: EVINRUDE & JOHNSON 40HP 1984 - 1988 EVINRUDE & JOHNSON 40HP 1996 - 2001 EVINRUDE 40HP 2004 - 2005 EVINRUDE & JOHNSON 45HP 1986 - 1997 EVINRUDE & JOHNSON 48HP 1987 - 1988 EVINRUDE & JOHNSON 50HP 1971 - 1975 EVINRUDE & JOHNSON 50HP 1979 - 1988 EVINRUDE 50HP 2004 - 2005 EVINRUDE 55HP 1976 JOHNSON 55HP 1976 - 1981 EVINRUDE 55HP 1978 - 1981 JOHNSON 55HP 2003 - 2005 EVINRUDE & JOHNSON 60HP 1980 - 1982 EVINRUDE & JOHNSON 60HP 1984 -1985 EVINRUDE 60HP 2004 - 2005 A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression. Gaskets are normally made from a flat material, a sheet such as paper, rubber, silicone, metal, cork, felt, neoprene, nitrile rubber, fiberglass, polytetrafluoroethylene (otherwise known as PTFE or Teflon) or a plastic polymer (such as polychlorotrifluoroethylene). One of the more desirable properties of an effective gasket in industrial applications for compressed fiber gasket material is the ability to withstand high compressive loads. Most industrial gasket applications involve bolts exerting compression well into the 14 MPa (2000 psi) range or higher. Generally speaking, there are several truisms that allow for better gasket performance. One of the more tried and tested is: "The more compressive load exerted on the gasket, the longer it will last". There are several ways to measure a gasket materials ability to withstand compressive loading. The "hot compression test" is probably the most accepted of these tests. Most manufacturers of gasket materials will provide or publish the results of these tests.