How do you determine the year of a Honda outboard motor by the serial number Locate the serial number. Look around the side of the outboard, just below the widest top part of the motor. If you cannot locate it, call a Honda Marine dealer for assistance. Find the two digit letter or letter and number combination around the middle of the sequence, just after a number that corresponds to the horsepower of the engine. For example, if your serial number has the following format XX2. A3. XXXX, 2. 5 indicates the horsepower amount, and A3 indicates the year built. Classic Triumph Motorcycles to be featured at 2012 Barber Festival 1022012 124913 PM. Triumph motorcycles will be the featured marque at the. Free Motorcycle Shop Manuals and Parts manuals Online.