Low speed problem, at wits end

79 Ski Tique
302 Ford Commander
Holley carb

Sat for years because it was unreliable.
Got it out and rebuilt the carb over the winter, tuned up and added electronic ignition.
Never idled great and would die at slow speed.
Worked with the idle mixture screws, seemed to help for a minute.
Eventually got to the point where it would not idle or run at all. Took it to a mechanic who checked fuel lines etc and said it idled when he lowered the front if the trailer to level the engine so he adjusted the float bowls (older carb so you have to do it manually).
It idles now but as soon as you put it in gear it will stall. You have to feather the throttle continuously to run at low speed and it will still die every few minutes. Smells like it's flooding.
Unfortunately, our place is on a channel so it is a long, frustrating ride through a no wake zone.
Messed with it pretty much the entire summer, it's just sucked good money after bad.
Any ideas?

I have the same problem on 78 Southwind. 351 Windsor with rebuilt Holley carb. Carb has been on engine about 4 years. Has a wedge plate to help level out bowls. Waiting for end of season to rebuild.

Also consider that other ignition parts could be worn, like plugs, plug wires, & coil.

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