Mercruiser 160 fuel pump return loop

[Alasknflick]

I have a 1969 mercruiser 160 with the GM 250 inline 6. This boat looks like it was loved by somebody and done right for some years and then another owner did some janky stuff. In the attached picture of the original parts diagram of the fuel system it shows a return loop around the fuel pump. My boat does not have the return loop. So I’m trying to figure out if this item is removed by someone who knew what they were doing or by somebody who was clueless.

Is this a safety of ship item that I need to reinstall? I am not a carburetor guy and this is my first power boat. If you know the reason for the loop I’d like to understand it.

 

[alldodge]

The line was used to help with starting. Many of the older fuel pumps did not have a check valve in them and after the motor was shut off, fuel would drain back over time. To prevent this a check valve and line was installed on the inline 6 cyl

The newer pumps are better and don't need it

 

[Alasknflick]

Awesome, thanks for the answer that makes total sense now.