As others have already said, the pistons are in upside down. As you described earlier, a typical symptom of this condition is that the motor may start but will not rev up and has little or no power.
Given that these motors were worked on by somebody with at least some ambition (if not technical skill) it makes you wonder what they were paying attention to when re-assembling what they ostensibly had taken apart. I can recall at least four motors that I’ve worked on where this condition was discovered, including a 7.5 hp Merc that dated to 1977. It was the worst of the bunch inasmuch as it would not even fire once under any circumstances even though the compression felt acceptable.
Another was this Johnson BN 
It was purchased from a collector who apparently knew what he was doing when he worked on motors. I guess anybody can have a bad day. I owned the motor for almost 20 years before I tried starting it. It would run on the stand but would not in the tank. That led me to digging into it to find out why. Looking through the spark plug holes gave the answer in a hurry.
at least it wasn’t a ton of work to correct it 
The next day she was out on the lake
https://www.youtube.com/watch?v=REnCyf-_SoA
You’ll get it corrected soon enough I think.
Best,
PM T2
He's livin' in his own private Idaho..... I hope to go out quietly in my sleep, like my grand-dad did..... and not screaming, like the passengers in his car...
