Re: End of My Rope...Fuel Problem
"Carbs were rebuilt by a good boat mechanic"
Perhaps not good enough to rebuild 'em properly.
When it runs with your introduced fuel, electrical issues are essentially eliminated. You've done everything to address any fuel delivery issues. (tho' you didn't say whether, after you pump up the bulb, that you have ensured that the carb bowls have fuel in 'em)
I suggest a lengthy dunking of the disassembled carbs in carb cleaner, if possible, in an ultra sonic cleaner.
That might still not be enough because a '71 engine has almost certainly endured long periods of inactivity, and an idle carburetor is corrosion's workshop. Corrosion can block passages much better than can ordinary gasoline gum.
The drill bit bit is a very good suggestion, and one that I'd try along with the less intrusive cleaning.
It might also help us -- Admirals and kibitizers alike -- to know when the engine last ran well (on carburetors) if you know, and the circumstances under which it quit, if it did.
"The mech that rebuilt these carbs had rebuilt my buddies tower of power and did a great job with it. "
A blind hog finds an acorn every now and then. But not always.
