Most marine carbs have J tubes for the bowl vents and the nipple on the air horn or carb body for the mechancial pump overflow.
Rochester Q-Jets don't have a J tube but the tube is cut in such a way to keep gas overflow from running out of the carb, it is facing the venturis.


in this pic you can see the nipple for the overflow tygon hose right above the carb fuel inlet....

in this pic of a Holley 4160 you can see the J tubes for the bowl vents and the nipple for the overflow on the air horn next to the throttle lever. If you blow this pic up you can see the stamp for marine approval on the air horn....
with remanufactured carbs you have to be very careful, it is actually better to rebuild what you have if the carb is in good shape internally.
Ironically I have seen new Quick Fuel marine carbs that have J tubes but no nipple on the air horn. They do have a vacuum fitting on the throttle body though.