check the plugs. If they are dark black then you almost certainly have
an ignition problem. coil points, etc. I had an old 1970 60hp
evinrude and they were just starting to use electronic iginition and it
took them a while to get it right. Anytime I tried to solve the
problem any other way I always landed back with ignition. That oil
laden fuel mixture is hell to ignite.

have fun.