The 50 horsepower (HP) Johnson is an outboard motor sized for medium- to larger-sized boats. The fuel pump on the outboard is responsible for pumping fuel from the gas tank to the carburetor, which in turn powers the boat and enables it to accelerate when the throttle is increased. If the Johnson sputters while it is running at higher speeds, it could mean that the fuel pump is going bad. There are some ways to determine this for certain.
Run the motor and squeeze the fuel bulb attached to the gas tank. Listen to hear if the motor smooths out when you squeeze the bulb.
Turn the engine off and unlatch the Johnson engine cover. Remove it and set it aside.
Remove the fuel line running from the gas tank to the carburetor with a screwdriver. Remove the inline fuel filter with pliers.
Turn on the air compressor and blow out the line with a hand-held air attachment.
Attach a new inline fuel filter to the line. Attach the line back to the gas tank and the carburetor. Also use a screwdriver to pry the fuel pump bulb off of the fuel pump. Clean out the mesh filter there with the screwdriver (or by hand) and then replace the pump's bulb by snapping it back into place.
Re-start the Johnson outboard and allow it to run at a high speed. If the motor still falters or sputters during this high speed, it means that the fuel pump is bad and should be replaced.
- "Evinrude/Johnson Outboard Shop Manual 48-235 Hp, 1973 1990 (Clymer Marine Repair Series)"; Randy Stephens; 1991