2004 40 gets spark in all 3 but does not combust

I have a 2 stroke 2004 40 and it does not have a ton of hours on it and is in generally good shape. The 3rd bottom cylender is getting good spark and smells "gassy" but is not combusting so the engine has no power.

Could the carb for the bottom only be clogged/blocked? They were rebuilt last year and I am not sure how good a job was done. Boat ran fine all season and then sat for a few months at the end of the season. Was having problems with a tempo fuel tank at the connections (not sure if ethenol had damaged the tank it was only 5-6 years old) but did not seem to run right at haulout.

How hard is it to pull carbs/rebuild myself and does it make sense to replace them? What should I expect to pay for new carb set if so? Any other obvious things I am overlooking?

Thanks for the replys.

[jb123]

spray bottle with gas, spray in throats while trying to start.

Maybe a dumb question, but straight gas or pre mix?

Thanks

spray bottle with gas, spray in throats while trying to start.

Perhaps I should have mentioned, it starts right up and idles relatively ok on what appears to be the top 2 cylenders.

[jb123]

then try a finger in the dry cylinder, simulating choking and see if that helps... if SO then thats the carb that needs cleaning

[jb123]

im not familiar with the smaller motors but they must have somewhat the same fuel pump as the larger, if you have excess fuel in cyl it may have a bad diaphram.