If you own a Mercury outboard motor and plan to rebuild it, modify it or service it, you must first gather some essential information including the model year to make sure that you purchase compatible parts as needed. You can also follow these steps if you're just curious to find out how old your Mercury motor really is.
Stand with the propeller end of the motor pointing toward you and look at the right side of the motor mount assembly.
Locate the serial number plate. The top number on the plate is the serial number, but the number directly beneath it is the four-digit year of manufacture. If you cannot find the plate, refer to the first link in the Resources section of this article for a visual aid. If the year is not legible, proceed to the next step.
Navigate to the second link in the Resources section and look up the serial number of your motor. The serial numbers are arranged by horsepower, so you will also need to check the horsepower indicated on the outside of the plastic motor cover. On the chart, you must look for the two serial numbers that your serial number falls between. When you find them, look at the year indicated on the line of the lower number. This is the year of your motor's manufacture.