Backfiring

"I have a 3.0L 4cylind 2 barre

"I have a 3.0L 4cylind 2 barrel carb 2005 merc. The engine runs great but when i am in rough water i will experience loss of power and a backfire when i am between 2000 and 3200 rpms. If i give more gas it will regain power. if i do not give it gas it will sputter and either stall out or regain power. If it stalls out restarting usually is a cure. In either case (stalling out or more gas) once i get it going it runs great without any further problems. I have changed all of the 3 fuel filters (water seperator, full pump and carb). The common thread for when it happens seems to be sea conditions not length of time run, temp. I suspect some water in the gas. What do you think?"

Did you find any water in any

Did you find any water in any of the filters? Any other schmeg?
You may have a pool of crud in the bowl of your carb that gets stirred up in rough water.

Rod

sounds like your float is out

sounds like your float is out of spec inside the carb and/or in rough seas it runs out of fuel.

"I have changed all the filter

"I have changed all the filters. The one on the carb. was clogged with gunk so i replaced the filter. I did take the carb. apart and it was, to my surprise, clean. I did look at the float and it seemed to be in good shape. Based on the foregoing and your points do i am starting to believe that i have some bad fuel laying in the bottom of the tank, which was replaced 1.5 years ago. WHat do you think? If you agree are there any additives that may help?"

Startron fuel additive removes

Startron fuel additive removes water to a point. SEAFOAM dissolves varnish and gum in the entire fuel system.