1971 Johnson 125HP outboards Service Manual, Page 101Get this manual
SlflFT CIRCUIT CONDITION REASON Shift toggle switch Shift solenoids Engine wiring Shift diodes Rectifier assembly Blocking diode
1Cannot shift out of forwardJumps out of neutral or reverseBurned out blocking diodeBlown fuseno apparent reason
2Lower unit "shifts" into forward before engine sto'p when
key is turned off
3Cannot shut engine off
TROUBLE SHOOTING STEP 1SHIFT SELECTOR SWITCH aConnect 12 volt test light between green lead ill and common engine groundbKey switch onShift lever in neutralcLight should lightdRepeat test at blue lead Use shift reverse pqsitioneIf no light at (D or move test light to purplegreen lead at terminal blockfIf light lights, shift toggle switch badgIf no light at purplegreen terminal, check blocking diode, ignsw, fusebattery
STEP 2BLOCKING DIODE akey switch off positionbConnect one ohmmeter lead to purple lead G)Connect other lead to purplegreen lead shift switchcUse high ohm scalenote readingdReverse test probesnote readingeOne high reading, one zero reading, blocking diode okfBoth high readingsdiode opengBoth zero readingsdiode shorted