Can't get off dock...
This winter I posted about my new engine never being able to get out of the harbor at idle. Had to "putter out on the kicker" to open water then hammer the main engine to get going and clean it out... Lot's of thoughts about "air" in the doghouse and "cold freezing" in the carb, etc, etc.
I promised I'd let ya know if I figured it out; It was the choke! It seems pretty simple. And yes, I feel pretty silly not having caught that in the first place. But it did it from the first start up after the new engine went in, so it didn't seem logical. Basically, wasted tons of gas and two seasons of stress trying to determine the cause.
Solution/diagnosis; Bungee cord on the choke to keep it from sticking. It would "load up" thus, we went down a rabbit-hole thinking it needed air and that the spark arrest was gumming up, leading me in another direction looking for the solution.
New engine; Mercruiser 350 Chevy block
Old engine; Volvo 305 Chevy block
Thank you to all who posted their help and support.
Check your choke pull off. The diaphragm in the choke pull off is probably broken. This keeps the choke from opening about 1/4" while the choke coil warms up. I am assuming a Q jet carb.