Carb has to come off and come apart. a lot of the marine carbs use a small nylon/rubber tube as a fuel passage inside the carb from sort of a foot sump up towards main jet. Not uncommon for the tube to give way to age, split or break at a connection point.
It's an older motor Dave. Wouldn't surprise me if you're right on this. Maybe it's time I taught my self how to tear down and rebuild a carb.
