FORUM RULES UPDATED - The forum rules have been updated to continue to provide a friendly and safe environment for our member community. Please take a moment to review the updated rules and our terms of use and privacy policy. Click here for Forum Rules which has links to the 'terms of use' and 'privacy policy'.
I think the number is a part or casting number. That vintage Merc should have a serial number plate on the tilt tube housing. Also the serial number may be stamped as shown below. Not your motor, but may be similar.