Re: 1991 50hp force no spark on bottom cylinder, coils are good. What to check next?
A couple of things to check before you go out and purchase parts. Make sure all of the spade lug connectors from the stator, CD Modules and Trigger are making good contact on the terminal strip.
If the spade lug connectors have a small piece of black heat shrink covering the spot where the wire is soldered to the connector, tug gently on the wire. Sometimes the wire will break inside the insulation giving you the impression that the wire is intact, when in fact it is broken. The trigger wires are more susceptible to breakage as they are smaller in diameter.
Double check the stator resistance. Not likely the stator but a good idea to check and be sure. Disconnect the Blue and Yellow stator wires. You should read between 680 - 850 OHMs across them.
Make sure all of your ground wires from the coils and the CD Module and between the coil/CD Module mounting plate and engine block are in place and making good contact.
If all checks out OK, then the CD Module is the most likely culprit. From what you describe, it sounds like you have the Prestolite ignition system that uses the Light Blue CD Module and coils. Best price I've found for new ones is here. I've ordered from these folks and they have very good customer service.
Force Outboard Power Module 92 5104 | eBay
