The clutch dog is located in the lower unit gearcase. It’s the shifting device that moves back or forward along the prop shaft to engage the forward or reverse drive gear. The clutch dog has "ears’ on it that engages the drive gears and over time, the ears can be worn down to the point the gears slip and grab when under load. See picture enclosed – yours may not look exactly like this one but you can see the ears.
If you replaced all the ignition parts, you should have replaced the wires as well. Considering those may be the original wires, they are over 50 years old and may have cracks that allow spark to go to ground. Try running the motor in the dark and look for wire arcing. Also check where the wires come out of the magneto plate to see if the wires are chafed – you may see a burn mark on the mag plate.
Attachments:
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1957 Evinrude 3022
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20
1982 Evinrude 25hp
“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."