How sick is this motor ?

I ran a compression check on my OMC 350 and found the #8 cylinder was 130 psi, all the other cylinders were between 145 and 155. I did not have the motor warmed up when I checked the compression like I should have. The plug from the #8 cylinder had some black gunk built up on it, the other plugs looked good, kinda brownish.

I put eletronic ignition on it this spring and I have a mid RPM miss above 3000 RPM goes away at WOT. Could this low cylinder be part of my problem? Everything else in the ignition system is new or fairly new and in good condition.

how bad is it?

I am not sure, I have had the boat starting on my second season. I looked through the old service records and the motor was replaced with a long block in 1993. The boat hour meter reads ~ 434 hrs. My guess the long block was a remanfactured block that the marina used to replace the bad existing block.