Can weak coils cause motor not to idle?

[Lamarg33]

Does anyone know if a weak coil can cause a motor not idle?

The motor is a 1967 6hp Johnson. To get it to start, I have to close the choke and open the throttle all the way. It takes two or three pulls to get it to fire. Then I can open the choke and pull a couple more times until and it starts. It runs strong with the throttle opened. But if I back off of it to idle, it spits and sputters and dies. I have to repeat the process each time it dies. I replaced the points, condensers, plugs, fuel pump, and rebuilt the carburetor. And nothing has helped.

Today, I hooked a spark tester to it and found that the spark on both cylinders is red-orange. Oh, and the compression is 100 on both cylinders.
So can this be the coils? Or have I missed something. I will greatly appreciate any advice.

 

[Daviet]

Re: Can weak coils cause motor not to idle?

Yes, coils can cause weak spark. Remove the flywheel and check to see that the coils are mounted properly, coil laminations are even with the bosses on the mag plate. Make sure your points are set properly (.020), and recheck the spark. If you still have weak spark, replace the coils.

 

[F_R]

Re: Can weak coils cause motor not to idle?

I would guess it is the carburetor. Focus on the idle circuit. That would include the slow speed adjusting needle, and the ports below the core plug.

Is the needle flat on the end or a sharp point? If flat, the end may be twisted off in the seat.

Could be incorrect spark/carb sync too.

One last thing: So are you running it in a tank or on a boat? If in a tank, do you have the hood off? Don't expect it to run with the hood on.

 

[Lamarg33]

Re: Can weak coils cause motor not to idle?

The lean/rich screw does have to be turned all the way out for it to run. It will actually run with the screw completely out. If I tighten it until it just gets snug and then back it out 1 ? turns, it will run. But if I try to adjust it in just a little it dies. I checked the tip and it still has a sharp tip.