Mercury 2005 50hp elpto 2 stroke sneeze issue

Hello and thanks for reading my post. I have the merc listed in title. The engine at medium idle (at apx 1700 to 2200 RPm) had what I thought was a lean pop or sneeze. When I decided to look at adjusting the idle jets, I noticed that the back fire was able to be seen on the engine side of the block between the carb and engine block. (The spacer between the carb and main block) there is a gasket on each side of the spacer. On the engine side I am seeing a flash on the top carb in at the gasket every time it pops/sneezes. I am assuming that the gasket is bad.Here is some side notes I just had a carb job done on it about six months ago and I've had problems ever since I did it. The company that did it had never contacted me back when I called them multiple times to try to see if it could be fixed. I have since moved away so there's no way to bring it back to them. Some other issues the engine has been experiencing are as follows: Engine stall- while in the water and on plain, the engine will start to bog like its starving from gas. If I squeeze the squeeze bulb it will pick back up. Idle adjustment of the top carb (while on the hose) seems to do nothing if I adjust the idle adjustment screw all the way in while running. Idle seems to stay the same. I looked at the plugs and they all seem to look the same. (None are gas soaked clean)Also, when on the water and at full throttle, I notice the engine drop off a little and pick up again (back and forth) all the time. 1st question. Why would I be seeing a flash on the carb side at the gasket. Is it just that the back firing has just torn the gasket and is not going out the carb? (I have not removed the air filter to see if the back fire comes out the carb as well. 2. What would cause the backfire. The gasket (allowing air in?) or something else.3. Why would it seem that adjusting the idle screw all the way in would not effect the motor. (Make it stall)Any ideas are appreciated. Just want to kno what to do when I bring it to the next mechanic.

You could have a busted reed petal(s) on your top intake.

The (blowback) could result in the toasted carb gasket (which you seem to note) - and if the reed is chipped/broken the air/gas/oil that should be getting forced into the cylinder gets (mostly) blown back through the carb throat since that's the "easy way out" for the pressurized mix (so you have one cylinder "possibly" not functioning or severely restricted which would account for the crappy idle, stalling, lack of power etc).

At minimum you have a bad gasket that needs to be addressed. When you get the carb off you will be able to get a look at the reeds.

The lack of response from your place of service might tend to indicate that they jiggered something up, were aware of it and weren't stand up enough to correct it.