78 Evinrude 140hp....Power packs? Coil? Plugs?

Engine stalled when progressing from idle and had to push automatic choke to keep it running and that worked. Local mechanic can't find problem and said I had a bad power pack. I replaced them both and it ran great for three weeks. Now, one of the new power packs appears to have failed. I switched sides with them and back again. Idles rough and sputters at high rpm. Can't see spark in one plug but engine responds when wire is back on it. Lots of blue exhaust smoke when testing plug spark. Could it be coil and plug wire failure? Or, plug(s)? I hate to buy another power pack and it fail because something else is making them fail. Anybody know what to tell me to do?

Re: 78 Evinrude 140hp....Power packs? Coil? Plugs?

My bet is a coil. I'll bet you can see cracks in at least one of them. If there is a crack between the metal laminations and the coil, spark can leak out there instead of getting to the sparkplug. Move the coils around and see if the problem travels with the coil. If not, then I'd suspect the power pack

Re: 78 Evinrude 140hp....Power packs? Coil? Plugs?

Welcome to iboats Randy!

Let's start at the beginning. Usually, pushing the auto choke to keep it running points to a fuel problem....likely a fouled carb(s). The idle circuit can get fouled and pushing the auto choke forces fuel to come up through the high speed tube.

Do you know if the engine sat for a long time before you aquired it? History helps.

Here's an easy way to check spark....take a 10penny nail and cut the head off. Stick it in the end of the spark plug wire. With insulated pliers, hold the pointed end of the nail 7/16 to 1/2" aways from a clean engine ground. Have a helper crank the engine. You should see a hot thick lighting like spark. Do this for each cylinder. If you get spark at all cylinders, I would consider overhauling the carbs.

I would also consider getting a service manual (OEM prefered) and reading it. It will help in troubleshooting problems and repair.

Again, if you can give us some history on the engine, that will help.

Thanks!

Re: 78 Evinrude 140hp....Power packs? Coil? Plugs?

Hi Randy,
I agree with OBJ on this one, about the carbs.

Another thing to check is the grounds for each coil. Someone had placed the ground wire terminals between the coils and block on mine and they tend to corode when placed there. Unbolt the ground connections and clean the terminals good. A faulty coil can cause a powerpack to fail.
Oh yea, and Welcome.
jimmy