No Spark - where to start?

I have a 1964 Johnson Seahorse 9.5HP model MQ-10R project engine. I picked this up just to teach my son about engines and working on them to get them running. The first thing I showed him was to test the engine for spark. There wasn't any. Before I go and show him how to pull the flywheel off (I'll need to buy a puller so I want to ask first), my gut feel is that the coil/magnetos are probably no good. Anyone have experience with this model engine and have a good idea what typically fails on them to prevent the plugs from firing?

It also has a kill button which I disconnected but still no spark. Not sure if it needs to be connected or not to get spark, anyone know?

All in all the engine looks good and mechaincally the shift, gears, throtle all appear to work fine, just no spark.

I have no real use for this engine, just showing my son how they work, so I do not want to invest a lot into it. I had an old 58 18HP engine a long time ago that I had to rebuild and I used boating, so I am familiar with outboard engines. Just looking for some quick direction on this model.

Please let me know
Thanks

Re: No Spark - where to start?

Well, whatever is wrong is sure to be under the flywheel.

Coils are suspect in that era of OMC engines, but they don't usually fail in pairs. My own experience is very limited on the low profile engines but suggests oily points from an imperfect top crank seal or dried out condensors.

It helps that there are two, mainly independent magnetos. They share only the flywheel magnets, the points cam and a kill switch circuit.

There has to be some way of isolating the two sets of points from each other so they don't ground each other through a kill switch. I don't remember how they did that, but it could be a source of both mags being dead.

Re: No Spark - where to start?

The kill switch shorts the two sets of point together to kill the motor. As said, pull the flywheel and take a looksee. All we can do is guess

Make sure you reinstall the flywheel correctly or you can destroy the motor. That means have the tapers clean and dry and use a torque wrench to tighten the nut to 40-45 ft/lbs. Don't tell me you can guess the torque within 5 ft/lbs by feel.

Re: No Spark - where to start?

I recently bought a johnson 10hp, 1959, no spark,
pulled the flywheel and both coils were falling apart, it made diagnosis easy enuf. You may find the same problem.
I used a harmonic balancer puller and bought hardened bolts at ace hardware.
Don't expect the flywheel to pop right off, give it time and work it by tapping the puller center bolt and tightening, leave the nut on loose or it might fly off.

Re: No Spark - where to start?

Thanks for the quick replies. We'll try the harmonic balancer to pull the wheel then go from there. It will be a while before I post any results if anyone is interested. As I stated its just a side project.

Re: No Spark - where to start?

Same thing as your old 18 hp...replace the coils/points/condensors and plug wires, or just look over the younster's shoulder while he does it. Then do the LU pump/impeller together...great project for both of you.

Re: No Spark - where to start?

Everything Under The Fly Wheel Can Be Replaced For Less Than You Might Think From Iboats.com . If The Coils Are Good You Can Get A Tune Up Kit For Even Less. I Like To Pull The Flywheel Just Once! Be Sure To Set Contact Points At .020 And Spark Plugs At .030. That Is A Good Thing To Do With Your Son