Last year I bought an old boat with a 55 hp, twin cylinder. Idled fine but
wouldn't open up. Rebuilt carbs and discovered that two screws came off
the air box and were sucked into the reed valves on one carb, holding a reed
open. Fixed that and engine ran fine. But next week it was back to
stumbling and killing when throttles were opened up. Due to floods, I just
got a chance to pull the shroud and look around it. I see a hose (vacuum?)
that runs from the front of the engine housing (intake manifold) to the back
of the air box had pulled loose from the air box (or I had forgotten to
attach it firmly). Any idea of the function of this hose and the
ramifications of it not being connected correctly? My shop manual doesn't
refer to it or show it.

Tom.