1980 Johnson 4HP Service Manual, Page 17Get this manual
TROUBLE TROUBLE
CHART (CONT)
POSSI BLE CAUSE SPARK PLUGSSee Section inner terminal damaged (spark plug terminal out of lead) Faul ty Ieads Looselow torque Incorrect heat range Defective (cracked insulator)See Section Loose broken wiring Charge faulty Sensor faul ty Loose armatu re pl ate screws Power pack faul ty MOTOR ADJUSTMENT Incorrect tilt angle CAV ITATION OR Protruding hull attachments Kee too long ransom too high Improper load distribution Marine growth bottom Added weight (water absorption) Mismatched and motor (boat underpowered)
MOTOR MISFIRES (Providing Fuel SystemCarburetor
4POOR PERFORMANCE ON (Providing Motor Runs
WEATHER AND ENGINE PERFORMANCE
The horsepower ratings of all motors those that would obtained under ideal conditions However, weather and altitude will affect the performance of outboard motorSome factors that will decrease the output of motor Low High High High barometric pressure temperatures humidity altitude