No Spark

[Nardo1895]

1984 Searay Cuddy Cruiser with a 350 Mercruiser. I'm trying to get my boat running again after sitting idle for a couple years. I replaced the batteries but I could not get the starter to work. Kudos to AllDodge who correctly suspected it was corroded battery terminals, most likely the ground stud on the engine.

Thanks to AllDodge I got the starter working but I have no spark. I cleaned all of the terminals of the main engine plug and every other terminal I could find that had anything to do with the ignition circuit but still no spark.

This boat has electronic ignition. It may have been a PO upgade, not sure they came this way in 1984. If it had points and condenser I'd try replacing them but not sure what to do at this point.

Thanks

Any suggestions?

 

[nola mike]

Start with 12v to the coil... Next depends on what kind of electronic conversion. Are you getting spark off the coil tower?

 

[Nardo1895]

My bad, yes there is 11.8 volts at the coil. I'm not sure what you mean by "coil tower". If you mean the where the coil to distributor wire connects to teh coil, I dont beleiev I have opower there. I tested it using a timing light and I got no light when I was cranking. Odly enough, when I stoped cranking I got a light flash.

My local boat shop told me electronic ignion wasn't installed in 1984, but this sure looks like a factroy installation. It is a Mercruiser "THUNDERBOLT IV".

 

[Nardo1895]

Opps, hit send to soon. Sorry for typos. The air cleaner cover also says "THUNDERBOLT IGNITION" so unless that was replaced too, I think its OEM.

 

[nola mike]

Sure sounds like it. Might want to start reading here:
https://forums.iboats.com/forum/eng...-mercruiser-thunderbolt-ignition-systems-work

 

[Nardo1895]

Great troubleshooting guide, thanks for linking me to that. When I get to the step that involves disconnecting the red/white wire I get odd results. I measure 5 volts.

I also have another electrical issue. I have partial function at the dash (running lights, gauges, trim) but some do not work (cabin lights, dash lights, horn, blower, bilge pump,...). I've checked all the fuses I can find and they are all ok.

I wonder if the two issues are related. The fact I have 5 volts at the distributor makes me suspicious of a bad ground. I swear I've cleaned every stinkin terminal, positive and negative, that I can find but I fear I'm missing one somewhere.