Some Good advice from some people that know there stuff.

I take it it's not common to do bore scope analysis on outboards?
I've got one cylinder with comression that is 14 psi lower than the others. And, I'm curious to know what is causing this.

I would be guessing but is it a lower bank thats low? Could be any number of things but most likely, a leak in the head gasket - retorque your head bolts to factory specs, could be worn rings, or if its been rebuilt in the past rings not correctly staggered --

14PSI isn't bad but I would try to find out why - do a static leakdown test with a good compression gauge

If you have a fiberoptic scope you can run the piston down and look at the cylinder walls thru a spark plug hole without popping the head

Not everybody has a bore scope . But anyone with a torque wrench can pull and replace a head gasket.

BTW.... Mine, with me doing it, requires a 3/8 drive torque wrench.
My 1/2 drive torque wrench does not fit, for a couple of the lower bolts. What happens though, is that you pull the head, and THEN you start wondering about the piston. So now, you might have to see what THAT entails (to pull that piston).

I can tell you you must remove powerhead off mid section and tear it down just like your going to rebuild it to remove one piston. BTW you would wonder this also with a bore scope view.

I had a guy that was going to remove one piston on a Looper 130 Johnson. He took of the carbs and took of the reeds, The rounded off the connecting rod bolts and the whole time, He was doing it in the wrong cylinder.....LOL

I only mentioned the bore scope in the context of a plausible explanation of the mechanic who said the guy had some scoring in one cylinder, and did it without pulling the cylinder head.

I had a 115 Johnson in the past with one cyl low. I decarbonized the motor with two cans of evinrude tune. One down the carb. Throats and one directly in the cylinders. I let it sit for 4 or 5 hours then ran the hell outta it at the lake. Did a compression test when I got home and the low cyl was back up. Must have been a stuck piston ring. I may have just been lucky but you may try it. Much cheaper than rings.

I ran a compression test on Friday and lowest was 106 and highest was 115lbs..Guess that still doesn't rule out a scored cylinder but it makes me feel better.