Sierra International 18-8353 Oil Seal The Sierra 18-8353 Oil Seal is interchangeable with the following: GLM 85840, Evinrude/Johnson 320961. Each Sierra product meets or exceeds the original equipment part it replaces. Sierra Oil Seal Meets or exceeds the original equipment quality Sierra part number: 18-8353 Interchangeable with the following: GLM 85840, Evinrude/Johnson 320961