Re: 1985 Evinrude 9.9 misfire

[Don]

Well, the engine is new to you, so we don’t know how it ran prior to the overheat…
Just want to be sure I understand what you are reporting…You feel the engine is running on just one cylinder, the lower #2 is not firing properly for some reason…But, you feel the lower cylinder is sparking "OK" because you feel/hear some sort of response when the #2 plug wire is pulled, even though RPM doesn’t really change. Do I have it right?
Well, sure you could have a water leak, doubt the head is cracked though…And, like Bill says, you will probably be able to see water droplets on the plug when you remove it…
Have you tried to run the engine at higher speeds in gear? If so, does the #2 kick in, or does it continue to run on just the top cylinder.
I guess I would go back to step one after checking the lower plug for water. Will then spark jump 7/16-1/2" gap while cranking? If so, did you try different plugs? Just cuz they are new, doesn’t mean they are any good. If all seems OK so far, you might want to try monitoring running spark with a timing light or those inline neon testers. If all seems OK so far, you might want to check compression again, perhaps something happened between the time you checked compression and now.
I can’t remember which cylinder the fuel pump is plumbed into, seems like it is the top cylinder, so it is no likely that a leaky fuel pump diaphragm in affecting the lower cylinder. I suppose you might have a broken reed, but that wouldn’t be my first "guess" and I would recheck all the simpler options before ripping the intake manifold off…