I pulled my plugs last night and the bottom one of the two seemed pretty gassy around the threads and the top one was not. When I had the motor running if I pulled the spark plug wires on the bottom plug the motor would stop but not when I pulled the plugs on the top one. I am not much of a mechanic. What should I do next? Is it time to take it somewhere. It's a 9.9 1974 Evinrude so I am trying to not spend to much money on it.