Specs of the 150 HP Johnson

by Amanda Gronot
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The Johnson HP 150 is a type of outboard motor, which is a self-contained propulsion system used by boats. It includes an engine, a gearbox, and a propeller or jet drive. Outboards move the boat forward and control the steering by pivoting left and right. The "skeg," or bottom flap, can also act as a rudder when the outboard is not running. Johnson motors were produced by the Johnson Motor Company, founded in 1921 by the four Johnson brothers. In 1935, Outboard Marine and Manufacturing Company (OMC) purchased the Johnson Motor Company. In 2001, Bombardier purchased OMC, and the Johnson brand was discontinued.

General Specs

The 2000 Johnson HP had 150 horsepower and displaced 158 cubic inches. Horsepower is a measurement of power that equals about 750 watts. The displacement refers to how large the engine is. The bore x stroke of this engine was 3.6 x 2.59 inches. The bore refers to the diameter of the cylinder where the piston moves up and down, and the stroke is the distance that the piston moves up and down inside the cylinder. The Johnson 150 had 6 cylinders, used a carburetor for fuel induction, and had optimal engine speeds of 4500 to 5500 RPM. It weighed 370 lbs.


The gear ratio, or the ratio of the numbers of teeth on the gears, was 1.86:1. It had FNR, or forward/neutral/reverse, gears. The gear shaft, which is the shaft that the gears are mounted to, was 20 inches long.


This engine had a 35 amp alternator, which is the device that converts mechanical energy to electrical energy. It used thermostat and pressure cooling. The steering for this engine was remote, meaning it was rigidly attached to the boat. The scavenging, which is how air at a pressure greater than the outside air pushes the exhaust gas out of the cylinder, was loop scavenging. This meant that the scavenge air loops around the cylinder and pushes out the remaining exhaust, rather than flowing in a unified direction.

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