starting problem sound like backfiring on 77 35 hp evinrude

[trav39562]

i just got a 1977 35 evinrude model number 35752h i didnt expect it to run but i turned the key and it fired up unexpectedly so tried to turn it of but the ignition didnt have the prongs for the magneto to kill the engine so i pulled the plugs off and it died. I cranked it back up a little bit later and it was running then all of a sudden it the motor jerked and died, now when i crank when it tries to fire if makes a super load pop i guesse backfiring. Has anyone heard of this?

[Cofe]

A motor backfire usually is caused by a sheared flywheel key. If it is, replace it only with a key from a evinrude/johnson parts dealer. Keys from hardware store will not work. Make sure to torque the flywheel at the proper torque or things could get a lot worse........

[edredfish]

A motor backfire usually is caused by a sheared flywheel key. If it is, replace it only with a key from a evinrude/johnson parts dealer. Keys from hardware store will not work. Make sure to torque the flywheel at the proper torque or things could get a lot worse........

i have the same motor with mine it was the head gasket

[MRneatfreak]

If it was running fine before, I don't think it is a sheared key, I think you have mixed up the plug wires? That is if you have two or more cyls? It will also backfire if there is a lean condition.