Late 80's Force 50hp by US Marine - intermitent spark

All,

I have a 50hp Force throwing a fit. Intermittent spark at best.
Pulled plugs, grounded them to the block, hit the key and cranked it over, after cranking for a few seconds the plugs sparked then quit.
Cranked again, nothing
Cranked briefly another 4 times - no spark
Cranked it the 5th time and the plugs sparked bright blue spark perfectly.
Installed the plugs, hit the key, motor fired up then I shut it off to resume diagnosis.
Pulled plugs, grounded then cranked the starter, no spark

This is where I am currently at with it, no spark or intermitent spark.

Thoughts on this one? Key switch? Loose ground wire (have not found one yet)? Bad coil under the flywheel? I cant imagine the CDI is all bad at one time.

Thanks!!

Re: Late 80's Force 50hp by US Marine - intermitent spark

You haven't gotten any replies so i'll try, but be forewarned, electrics is my weakest link. It's (the system) is trying to work, then giving up). I would clean all my connections, I mean, shiney metal to shiney metal, to put that possibility out of the picture. Then you're into more involved work and someone elses hands.

Re: Late 80's Force 50hp by US Marine - intermitent spark

Gotta know the year? Serial#?
The late 80's they had 2 different ignitions??
Pics of yours?
Outboard ignition . com or CDI ignition . com Both have test procedures for your ignition.
You'll need a meter to test the parts.
Do a compression test.

Re: Late 80's Force 50hp by US Marine - intermitent spark

Model # 507Y9B = 1989 It has all electronic ignition.

Thanks again!!

Re: Late 80's Force 50hp by US Marine - intermitent spark

As a follow up, I removed the flywheel to find the magnetic strip inside the flywheel had fallen off. It had been working loose for quite some time as it was pretty rusty under the magnet. I polished the inside of the flywheel and the magnetic strip, reglued it in place and the motor is running like new again.

Re: Late 80's Force 50hp by US Marine - intermitent spark

Cool that you found the prob. How did you find out what to do?

Re: Late 80's Force 50hp by US Marine - intermitent spark

I also have a 89 force 50 and when i had a intermittent spark problem it was my top coil then after running great for weeks it did it agen and then it was the bottom coil now a year later its great. I used two cheap spark testers from harbor freight and ran it in water till I saw the coil drop off. Is your motor the one like mine with the blue coils with long plug wires or the short ones. Also look at the wires near the cdi for damage.

Re: Late 80's Force 50hp by US Marine - intermitent spark

I had it figured to be something under the flywheel. Normally when all spark is lost to all plugs, that points me in the direction of something that would control the entire ignition curcuit. The trigger would be the first thing to question. Not knowing a ton about how a chrysler/force igntion system works, I compared it to something I do know about. OMC and Mercs. They all work on the same theory.

So... as I pulled the flywheel thinking I was going to be replacing the trigger.... There was the magnet strip! Cheap fix!!

Re: Late 80's Force 50hp by US Marine - intermitent spark

Ah So, good deductive reasoning.