Mercruiser carb question

I don't know if this is the right place to ask due to the fact that I drive a fakeboard boat, but you guys have been awesome and helped a ton so far. I have a 97 Maxum with a 5.7 Mercruiser and when I go to the lake It usually starts pretty easy the first time, but every time we stop for more that 2-3 minutes I have to fast throttle start it. The carb was actually just rebuilt a couple months ago. Anyway, today I am looking at the motor and see a yellow/clear hose attached to nothing below the carb. I take off the fire arrestor and on the back of the carb there is an outlet with nothing attached. Just wondering if this may be the source of my issue? I hooked it up made my fake lake and it fired right up, no throttle pumping. Then after about 5 min I shut it down and came back out to try again. It hesitated a little but ended up starting. Just dont want to hook something up I shouldnt have, but it definately looked like a fuel line and went on the fitting like it should be there. Just curious what some of you may think.
Thanks