Mercury 50hp Wont Start

[TheBigboater]

New here to the forum and looking for some advice! I have an older Mercury outboard, 50hp 3cyl 2 stroke. Serial # 0A987369. It ran fine a year ago, but I cannot get it to run now. I cleaned the carbs twice, new fuel, pump is working correctly, new plugs, and I know it is getting spark (Nice bright blue color). It will fire up and run for a few seconds, then it acts as if its having a misfire and backfires and dies. Im almost positive its a spark/timing issue.
My question is, does this sound like a bad trigger? CDI box? Someone mentioned a bad trim limiter could cause this? Im somewhat new to the boating world so any advice is appreciated! Thanks!