Issues with a 1989 Johnson 25 HP

Hey y'all. I'm very new to outboard motors, but I have tinkered with 2-stroke mototrs in the past. I got a 25HP Johnson (Model J25RCEM) with a boat I picked up a few months back. I ran the motor for the first time yesterday and it ran pretty rough. It won't stay idling at all. I have to keep tickling the throttle to keep it running. Also, it doesn't seem to get to max RPM. After I got back to the house, I took out the spark plugs and there seemed to be a lot of oil on the plugs. It sounds like a carb cleaning/fuel filter issue. Any ideas? Thanks in advance!

Old gas? I would guess clogged jet or fuel filter.

It was brand new gas. This is the first time I had the engine running since I bought it. The other guy said he ran it all the time, but he also said it was serviced last March. Both of those statements I highly doubt.

It's likely the carb as you indicated.
Since its a "new to you" motor, I would start with testing compression and spark.

how rich did you mix the fuel/oil? did you change the spark plugs?

How about we start with the basics instead of rebuilding things yet? You may end up putting a kit in it but lets start simply.
Your engine is equipped with an idle mixture screw located on the carb. From the sound of it you are running a little rich due to the fact you did not mention the engine sneezing and quitting at idle. Running rich will cause the engine to run rough and idle lower than normal.
You also should have an idle rpm adjustment on the engine whos location will vary depending on whether the throttle has a cable or is gear driven. Adjust your mixture screw inward or clockwise 1/8 turn at a time and let the engine adjust to the new mixture for around 20-30 seconds and then lean it more and wait again. Do this until the engine lean sneezes then back out around 1/4 turn and leave it there.
Incidentally, as far as the rich mixture comment on fuel/oil goes, you can idle this engine all day on 24:1 with no issues so not to worry on that.

Thanks for the input guys. I did a compression and spark check. Everything is good there. I know I'll have to clean the carb out (plan on doing this today. Pappy, I saw your post about 24:1 fuel/oil ratio. I put 50:1 in it. Maybe that's what the problem is? Can anyone confirm that it's 24:1 rather than 50:1?

No, your engine is supposed to run on 50:1 mixture.
That was added simply to let you know if it was a richer mixture not to worry about it.