Johnson Evinrude Outboard Motors 1956-1970 1.5-40hp repair manual., Page 263Get this manual
TROUBLESHOOTING with the shift cable disconnected, the problem must be in the lower unitTo verify the problem is in the lower unit, have an assistant turn the propeller and at the same time move the shift cable back-andforthDetermine if the clutch engages properlyJumping out of Gear
If loud thumping sound is heard at the transom while the boat is underway, the unit is jumping out of gear, the propeller does not have load, therefore the rushing water under the hull forces the lower unit in backward directionThe unit jumps back into gear; the propeller catches hold; the lower unit is forced forward again, and the resul is the thumping sound as the action is repeatedNormally this type of action occurs perhaps once day, then more frequently each time the clutch is operated, until finally the unit will not stay in gear for even short timeThe following areas must be checked to locate the cause: 1- Check the bellcrank under the powerheadThis is accomplished by first checking in the Appendix to determine the type of shift mechanism installed on the unit being