70 HP Mariner With A Miss

[tshaljr]

I have a 1980 70hp Mariner ob. Runs but has a miss about every 3 seconds. If I pull the plug wire off of the top plug I can hear it "clicking" and if I move far enough away the motor bogs down. Putting it back and the motor comes back. Same thing with the second plug. However, with the third plug I can hear the "clicking" but if I move it further away, there is no change in the motor. It continues to run with the miss. What is causing this to happen? Local guy says it is the switch. Could it be the wires?

 

[gm280]

When you remove the plug wires, what are you talking about moving it further away? Once you remove any plug wire, that should make the engine change RPMs. If it doesn't, that cylinder is dead, meaning not firing. If the RPMs do change, moving the spark plug wire further away (how far can you get it away?) then that cylinder was doing its job. So make certain every plug is changing the engine speed when you remove that cylinder's spark plug wire first. Then look for whatever else you are hearing. JMHO

 

[tshaljr]

I'm pulling the spark plug cap off of the spark plug just far enough away where you can hear the spark arcing to the plug and the rpm's do not change. If I move it further, about an inch, the arcing stops and the rpm's drop. Moving it back and the rpm's pick back up. This does this for the top two plugs but when I do it for the bottom plug, I can hear the arcing from the wire to plug until I move it far enough away that the arcing stops. However, on that plug, the rpm's do not change. What do you mean that the cylinder is dead? How serious is this?