1980 Evinrude 7.5 No Spark Bottom Cylinder

[Todd in NY]

As the title states, I don't appear to have any ignition in my bottom cylinder. The top one is firing as it should, and the motor doesn't sound off, but it's down on power.

Question is, how do I know or diagnose whether I should replace the ignition coil (#34) or the power pack (#11)? Both cylinders run off the same power pack, but each cylinder has it's own coil. I'm thinking I should replace the coil first, but I'm no mechanic. Any suggestions? Thanks!

 

[interalian]

You can swap coils by pushing their cables out of the rubber plug and swapping location in the connector, then swap the wires on the spark plug to prove coils. But first, try swapping the spark plug wires, then the plugs themselves. For reference, there are two orange wires coming from the power pack and one has a blue stripe. The blue stripe is for the top plug.

How's your compression?

 

[oldboat1]

Does it stall if you pull off the top plug boot while running?

 

[Todd in NY]

You can swap coils by pushing their cables out of the rubber plug and swapping location in the connector, then swap the wires on the spark plug to prove coils. But first, try swapping the spark plug wires, then the plugs themselves. For reference, there are two orange wires coming from the power pack and one has a blue stripe. The blue stripe is for the top plug.

How's your compression?

Thanks for the tip! The compression with the engine cold was 90 on top and 80 on the bottom.

 

[Todd in NY]

Does it stall if you pull off the top plug boot while running?

I haven't tried that yet, but great idea! I'll test that tomorrow, thanks.

 

[Todd in NY]

The problem was a bad coil. The motor runs great again after replacing the bottom coil.