74 Johnson 9.9 spark plug issue

TinBoats.net

Help Support TinBoats.net:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Gotem

Well-known member
Joined
Aug 31, 2012
Messages
122
Reaction score
0
My 74 Johnson 9.9 sounded like it was running only on one cylinder the other day. The first two time this year, it ran great. The third time it struggled like one cylinder was not firing. The other day (4th time) it worked like it had one cylinder firing. At home I figured out the bottom spark plug was working because when I disconnected it, the motor would quit.

Taking a look at the connection from the power pack to the top spark plug I noticed the coil in the boot that connects to the tip of the spark plug from the power pack was sideways. I also noticed that as I turned the boot the coil would turn with the wire and not the spark plug boot.

Any ideas on how to fix this? I tried several times to connect it to the spark plug so that they are aligned, but it was to no avail. Any ideas? Could it be something else?
 
Well.....Number one, I don't think that is your issue. As long as the contact on the end of the plug is even close to the coil inside the plug wire boot it should fire.
Second. You have no power pack on that engine if it is indeed a 1974.
Check spark. It should be able to bridge at least a 1/4" gap at hand crank speeds. If you think it is the coil (ignition coil not the plug wire coil) simply swap primary wires and secondary wires and see if the problem follows the coil or not.
 
I checked out a few tings with the motor. Compression was 109 and 112 psi. Cylinder 1 was misfiring. I replaced the coil Part 0502880 (on the box). It seemed to run good the first trip (which was short), but the second trip it was back to running mostly on one cylinder. Any ideas on what else it could be?
 
i recommend following Pappy's advice and doing a spark test with gap tester and then swap the coil wires and see if your problem follows... let us know your results and i'll try to help out.
 

Latest posts

Top