I run through the locations and as soon as I get to the location where the gun is installed on the boat, I can't pass through the wall with the help of a barrel or a coil, I just jump on the spot with it and that's it. Help.

The trick you are trying to do is called quickclip. As Nikitos mentioned, you need to do a trick called yesclip to be in a glitched state which allows you to do any quickclip. Here are two places where you can do yesclip in:

Current route, but difficult, since you cannot save delete at any point to keep the quickclip state, and the goo tunnel is quite hard for beginners:

Older, but easier route: