1995 Evinrude 40HP running on one cylinder

[bomar76]

1995 Evinrude 40HP
Model E40EEDD
SN G03909409

Symptom:
Engine runs on one cylinder
Story:
Engine runs on one cylinder, but will ocassionally second will kick in (usually higher RPM)....but it's not always same cylinder.

Saturday: Was only running on bottom cylinder. Replaced spark plugs, no change, swapped plug wire from top to bottom, no change, checked for spark at both coils, has good strong 7/16" plus spark. Removed carbs and checked for debris in fuel bowls. Fuel bowls both full of gas (always ethanol free), zero debris. No change. Replace primer bulb. Fired right up on both cylinders. Ran great.

Sunday: Now only running on TOP cylinder. Swapped plugs between two, no change, swapped wires, no change, again checked spark, still quite strong.
Put all back to original location and now purrs along on both cylinders.

So...I have not really fixed anything or even found an issue. The trouble does not move with swapping parts. New primer bulb. New plugs, Compression appears strong on both, did not check due to gauge being 100 miles away.

Ideas?

 

[Bosunsmate]

1995 Evinrude 40HP
Model E40EEDD
SN G03909409

Sunday: Now only running on TOP cylinder. Swapped plugs between two, no change, swapped wires, no change, again checked spark, still quite strong.
Put all back to original location and now purrs along on both cylinders.

Ideas?

So it was still only running on top cylinder when you had checked you had good spark on both?
Have you a timing light?

 

[bomar76]

Yes, always shows good spark on both cylinders.
Going back to lake Wednesday, will take more test tools

 

[bomar76]

Additionally, pumpimg primer bulb while running has no effect.

 

[Bosunsmate]

Yes, always shows good spark on both cylinders.
Going back to lake Wednesday, will take more test tools

might be powerpack going with irregular timing, good luck

 

[bomar76]

Thanks, had same thought

 

[gm280]

So if I'm understand correctly when the engine drops a cylinder, you verified both cylinders still had good strong spark? If so, there is no ignition issue. Next time take some 50:1 mixture with you and when it drops a cylinder, squirt some 50:1 mix in the drop cylinder's carb and see if that fires up again. If so, you have a fuel delivery problem...

 

[bomar76]

Yes, always have spark to both. Will try the carb squirt

 

[jakedaawg]

If I understand this sometimes you are losing the top and othertimes the bottom but you always have spark?

 

[bomar76]

Yes, sometimes top sometimes bottom.