1975 Johnson Coil Pack Problem?

[Nomad767]

Me and my brother are starting to think one or more of the coil packs are defective. So can anyone help us with this? The engine runs great until it warms up...we can run it pretty good for about 10-30 mins, then the engine starts to run rough and won't even keep it planed out. I hear that this usually indicates a coil pack. The fuel tank is a brand new portable unit and the vent is working properly. The exhaust starts smoking alot like it is missing once it starts doing this...sometimes it will do it, and sometimes it will clear up and do it off and on. Is there anything else that would cause this? Or are we on the right track?

Also, I was looking at coil packs online...anyone know about Sierra Aftermarket parts and ordering from a website called iShopMarine.com?

 

[sheboyganjohn]

Re: 1975 Johnson Coil Pack Problem?

From what I have read it sounds like you are on the right track. If you go to the main forum under the repair and maitenance group there is a FAQ section for motor repair. There is good info in there that may help you narrow it down further, or confuse you more depending on how technical you get with it. As for ordering parts you can order them from here at iboats, just use the marine store drop down at the top left. I have only replaced coils on one motor and that was two years ago with the seirra brand. They worked fine, but I don't know about the long haul.

 

[jonesg]

Re: 1975 Johnson Coil Pack Problem?

Put a timing light on the plug wires when it starts to act up, it does sound like coils and heat soak. I get my parts right here on iBoats.

 

[tashasdaddy]

Re: 1975 Johnson Coil Pack Problem?

it sounds like you are one the right track. you need to isolate the coils that are bad, as jonesg said timing light will work, but it needs to be done as soon as it starts to act up. but before replacing, swap the coil with one that is operating, to make sure it is the coil bad.
I believe you will get a better price, and faster shipping at iboats.com, the company that provides you with this free forum.

http://www.iboats.com/Johnson_Ignit...z.36857--**********.961189967--view_id.271400

 

[Nomad767]

Re: 1975 Johnson Coil Pack Problem?

Ok, Thanks for the heads up about the parts, but I am confused now. The CDI Coil listed on iboats for this motor, which is a 70hp, does not show a matching OEM# that it replaces. The OEM part# I have is 580821 which was superseded by OEM Part# 502890. My OEM Part# is listed under the 115hp coil. So which one do I need to buy? The one listed for this motor, or the one that matches the OEM# replacement under the 115hp?