Re: What is this tube for???
safety- in case the fuel pump diaphragm ruptures, instead of dumping fuel into the bilge, it dumps it into the carb through that hose... making the engine run rich and/or stalling it
there's a nipple on the carb that should be attached to - just slips on - but you can use a wee tiewrap if you want to help hold it
that section of hose on the fuel line with the 2 clamps doesn't look right to me... might want to check a parts book online somewhere - I think that should be steel line 1 piece from pump to carb.... I wouldn't trust hose clamped onto unbarbed fuel line.
keep that one in your tool box and tee a gauge into it for troubleshooting fuel supply issues down the road