1993 s stroke 40 hp low compression on lower cylinder

[Catmaster2018]

I bought a pontoon boat. Has 1993 2 stroke outboard 40 hp. Model C40PLRR. I have 120 psi on top cylinder and 90 psi on lower cylinder. I ran a inspection camera in there today both boats look good seemed smooth. Bottom piston is way carved up. I have ran 3/4 gas mixed 50:1 and 6oz of ring free ran it for 15min let it sit for 30 and did this until gas was gone. No help. Tilted to outboard up as far as it would go and squirted 5mm of ring free in the sparkplug whole with piston on top. Let it sit over night. Worked it back and forth a little bit and added another 5mm of ring free in there and sit over night. Nothing doing.
the outboard runs fine. Starts up quick and idles for about 7 min in the water before it dies sometimes it will not die. I can run it almost full throttle and runs great. If I put it at full throttle it acts like it is starving for gas. Guessing because the fuel pump runs on the lower cylinder. Any help to decarb this thing would be great.
thanks

 

[Catmaster2018]

I really never saw any real bad smoke after start up just normal 2 stroke smoke when decarbing

 

[rejesterd]

Low compression isn't related to carbon buildup. It's damage in the cylinder/piston or a leaking head gasket.

You can do a leak-down test to see where exactly it's losing compression (through the piston rings or the head), but whatever it is, it will be time-consuming and difficult to fix yourself (if you haven't done it before) or very costly to pay someone to fix (like more costly than the motor itself is now worth). You probably want to get a new engine or try some BlueDevil gasket sealer if you find that the leak is indeed coming from the head gasket.

 

[99yam40]

my guess is, If the bottom piston is way carved up then the metal being moved around has grabbed the rings

 

[Catmaster2018]

I looked in there with an inspection camera. The top is nice and flat just built up anti. And the bore looks good just like the top

 

[99yam40]

the rings are on the side of the piston that you said was carved up

 

[robert graham]

Carved up or carboned up?......