What does this wire do? (85 johnson 70hp coil)

[crazytegger]

I was looking over my motor today and I found a wire that was corroded or burnt through on one of the coils. It was the brown wire on the post directly above the post that the spark plug wire is connected to. The connector and post looked like they had a poor connection and had been corroded by arcing. Any insight would be great. I was ultimately trying to figure out why my overheat alarm was sounding. I can run the motor as long as I want with no alarm, but if I shut it off it will sound the overheat alarm next time I turn the key on. My guess is either I have a faulty sensor somewhere, or when the motor is not running, the water that is trapped in the cooling chamber heats up to "overheat" temp and then sets the alarm off. The alarm will go off about a minute or two after the motor starts running again. Any advice please?

 

[steveo32]

Re: What does this wire do? (85 johnson 70hp coil)

Do you know where the wire went to from the coil, if it is a short wire that went to the bolt that holds your coil in place then it is the ground, this wire is usually orange and brown. If it is a longer wire then it probaly goes to your power pack. My guess is that it is the ground wire. I just replaced a coil on my 1975 70hp and there is only 3 wires, one to spark plug, one to powerpack and one to a bolt for ground. It sounds like you will need a new coil, and that cylinder is probably not firing or is misfiring. You will probably have cracks on teh case of the coil too.

 

[Randyg123]

Re: What does this wire do? (85 johnson 70hp coil)

It looks like your engine has coils without wires on them, just two posts on a black plastic body. One post is where the spark plug cable connects and the other post looks like a spark plug connection only smaller. Is this correct? If so then there is no ground wire and the ground connection is made by contact with the engine. when bolted on. That means the other cable is your incoming voltage from the power pack. If this wire is not connect, you are not getting any power to the coil and thus that cylinder is not firing.

I am not familiar with these types of coils as my engine has the type that steveo32 was referring to with the two wires and spark cable fixed to them. Regardless, you've got to fix the wire, if possible.

Saturday AM is a tought time to get anwers really quick as the site is so busy. Hopefully this will bump your query back up to the top where an 'expert' will catch it and give you a better reply.

 

[crazytegger]

Re: What does this wire do? (85 johnson 70hp coil)

Thanks for the replies. There are only two wires: the plug, and the powerpack wire (the one that was corroded). I cleaned the post and replaced the corroded connector and the boat runs better now. I see some ignition work in my near future though. Thanks again, happy boating.

 

[mikesea]

Re: What does this wire do? (85 johnson 70hp coil)

If its a brown wire,and,your having heat horn trouble,sounds like your heat sensor wire is the wire in question,if it was a broken coil wire you would lose the cyl thus poor running,look for the sensor that the wire was connected to in the head