I am also not a pro mechanic, but will speak of past experience. Several times with an older Mariner 6cylinder with 3 carbs, it began to misbehave for no apparent reason. Tried many things with no change. Fuel cell was 23 gallons, and it got down to about an eighth of a tank of fuel and dumped a can of sea foam in. A lot of my trips were very close and never ran the motor over 5 minutes at a time. I did this til it was so low that the needle was lower than ever and didn’t wiggle at all. Put 12 gallons of fresh fuel in and had no more gremlins. My fuel was mixed with oil and I believe that I was getting some build up, and this helped remove it. Ran that boat ten years and put in a can of sea foam once or twice a year and never had to revisit my carbs. Good luck with it and let us all know what works for you when you get it straightened out.
Creativity is just intelligence fooling around