Johnson is one of the oldest and most recognisable names in boating. Johnson debuted its outboard engine at the New York Boat Show in 1922, featuring a 2-horsepower engine, which was revolutionary at the time. Early Johnson outboards, including vintage models from the 1920s through the 1940s, as well as models up to 1969, are identified using the model number located on the engine.
Locate the model and serial number for 1922 to 1942 Johnson outboards. According to the Yankee Antique Outboard Motor Club, both numbers are found on the top of the flywheel, stamped into the rope sheave. The top number is the outboard model number and the bottom number is a sequential production serial number.
Match the serial number to a Johnson model number identification guide, such as the one found on the Yankee site. The model number identifies the model code and horsepower designation. Model number AB-25 identifies the outboard as a 25 horsepower model AB, for example. The serial number represents the sequential production number for that particular year, each year beginning where the previous year left off. A reliable year designation can be obtained by comparing the serial number to a Johnson serial number listing.
Find both the model number and serial number on hooded outboard models. On early Johnson outboards which have an engine cover, or bonnet, the numbers are found on either on the front of the gas tank or on the bottom side of the engine block. This code and serial number follow the same pattern as 1922 to 1942 models; however, 1943 to 1949 models must refer to a listing similar to the one at the Marine Engine website (see Reference 4). This listing contains only model numbers, which are grouped according to horsepower designation, determined by the last digits of the model number. Outboard model year is also identified on this list.
Search the engine near the motor mount for the identification tag on 1950 to 1969 outboards. On the tag, the five-digit model number is present. The first two digits designate the horsepower, while the third indicates the last digit of the year of manufacture but not the decade -- since the model number does not identify the decade, it may be necessary to reference a model number listing similar to the ones found on the Parts Warehouse website (see Reference 2).