85 Johnson 70 HP no spark on bottom cylinder

[FrankMa]

My motor crapped out on me 6 miles out on Lake Erie the other day. It was first time on the water this year and it ran fine all the way out there until when I throtteld down I heard a grinding noise. Turned out that the starter gear was stuck up and engaged with the flywheel. Anyway after I shut it down it would not start again. Fortunately a good Samaritan gave us a tow back to the launch. I did a spark check today with a spark tester and I get good spark on the top two cylinders. Nothing on the bottom one. Swapped coils but still no spark on the bottom. Could I have fried something when that starter was engaged and being spun by the motor? What should I test next? I do have a multimeter but I'm not an electrical wizard so simple instructions would be appreciated. Thanks in advance.

 

[FrankMa]

I do have a Clymer Manual that covers this motor. I read the ignition system troubleshooting section and based on the observations made so far I tried the sensor coil resistance test. Supposed to get 17 +/-5 OHMS. I got 11 across terminals A-D, 22 across B-D and 22 across C-D. It says if you don't get 17 +/-5 replace the timer base. So I'm leaning towards replacing the timer base. Do any of you more experienced gentlemen agree with this course of action?

 

[racerone]

Sounds like a good approach.----A factory new or factory used in a good option.----Avoid an " amazon special " in my opinion.----Model # of your motor ?

 

[FrankMa]

J70ELCOS

 

[racerone]

Available right here on this page .----Just a few clicks and it might be rushed to your door step.

 

[FrankMa]

Thank you sir. I will report results when I get the replacement installed.

 

[FrankMa]

Turns out the timer base was OK. Found a better diagram that called out the terminals by wire color and it checked out OK. My original diagram showed a plug with a different configuration for the terminals. Anyway my flywheel key was sheared off and the power pack had no output to the wire for the bottom coil. After replacing the flywheel key and power pack I got spark to all 3 cylinders and motor runs fine. For the starter gear that stuck up and caused all the commotion I just cleaned and lubed the shaft and it seems to work OK now.