Re: 78 mercury 115 no fire
A 1978 Merc 115 has a battery driven CDI Ignition systems with a distributor. the first test is to make sure you have +12V on the red and white wires on the starboard side of the switchbox, when the ign key is turned on. No voltage=no spark. if that checks, look up the troubleshooting procedure at the CDI Electronics website.