94 60hp

My outboard won’t go past 3000 rpms in gear. When it is not in gear it will rev normally. I have checked compression and it’s 90 on all cylinders and idea what else to check

Is your tachometer reading correctly at idle in neutral?

Did it ever achieve full rpm under load? Need some history, if you have it. Was there a prop change. 90 psi is not too great.

There are all kinds of questions one could ask.
But the real question is how good of a mechanic are you? And how willing are you to get involved in something that could take many steps to diagnose?
If you are looking for a quick fix, there may or may not be one.
Let start with some better understanding of what the the real problem is.
Are you testing it in your backyard on muffs or with to boat in the water on the lake?
Most multi-cylinder 2 stroke outboards will run on less than all cylinders without a load (ie in gear on the water).
Let get some answers to some simple question.