1985 Mercury 75 hp no spark on 2 cylinders

[joshm]

Helping a friend with his new boat. He was told the outboard is a 1985 (serial is 6433329 which appears to be an 84), supposedly the stator was replaced just before he purchased the boat. Motor was running on 1&2 no spark on 3&4. Swapped coils 1 & 4, problem switched to 1 and 3 had spark 2 and 4 had no spark, so I assume the coils, wires, plugs are good. Is there any easy way to narrow down if the problem is in the cdi or the stator? I don't have a flywheel puller (I think I can borrow one if need be), and no donor/extra parts available.

Thanks for looking

 

[joshm]

Re: 1985 Mercury 75 hp no spark on 2 cylinders

My apologies, I miss posted. When I switched a known good coil (cylinder 1), with a non firing (cylinder 4) the problem stayed the same. 1 and 2 had spark 3 and 4 did not.

 

[OnTheWaterNow]

Re: 1985 Mercury 75 hp no spark on 2 cylinders

check the stator trigger and switchbox will need manual and dva multimeter step by step instruction and numbers are in book

 

[japayton6]

Re: 1985 Mercury 75 hp no spark on 2 cylinders

Go to cdi website can download troubleshooting guide will need meter I would bet power pack hope this helps

 

[joshm]

Re: 1985 Mercury 75 hp no spark on 2 cylinders

Got the troubleshooting instructions from CDI. Checked trigger coil leads, all were supposed to have 1v or more only the bottom two did which confirms why the bottom two cylinders were the only ones firing. The top two were .5v or less which would confirm why the top two weren't firing. However after reassembly, only cylinder 3 will fire now. Possibly trigger pack as well?

 

[japayton6]

Re: 1985 Mercury 75 hp no spark on 2 cylinders

check the wires on trigger old mercs bad about wires breaking down if so splice in new wires back to good wire

 

[joshm]

Re: 1985 Mercury 75 hp no spark on 2 cylinders

The bit could see looked good. I checked most of the wiring over because I found 2 leads from the trigger pack to ignition coils I had to replace due to being corroded almost completely through.