"Tom G" wrote in message
news:6v1tk.824$p72.2@trnddc05...
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.

Similar hose on our jet ski runs a diaphram fuel pump.