Re: ’51 Big Twin Home › Forum › Ask A Member › ’51 Big Twin › Re: ’51 Big Twin MumblesReplies: 5764Topics: 298 October 31, 2017 at 4:29 pm #66848 Here’s a diagram with original P/N’s for a ’51 Johnson RD 25 horse but I’m not sure though if Johnson and Evinrude were sharing parts on these motors back then. Attachments: