2001 Nordic Tug, two years new to me, can’t find any documentation explaining what this stalk is bolted on top of my fuel water separator assembly where I would expect a vacuum indicator might be.
Whatever was the purpose of that stack will likely remain a mystery. There is no telling for what it was used. Clearly, however, each of the joints is a point of failure. I would remove it all and install a liquid-filled drag needle vacuum gauge directly on top of that "tee".
It depends if it's on the tank side of the filters or the engine side. I would agree it's probably a cludge to replace a broken vacuum gauge. It might be some cludge to adapt a vacuum system to bleed the filters. Either way, it should be simplified or replaced with a proper vacuum gauge.
I have a big box at home with several of each of those fittings. The gage mounted there likely broke and the PO rifled they his box of fittings and came up with that to get back underway.
The difference is that I would never leave it that way. Too many leak possibilities as stated above.
( plus it looks like doo doo)
Surprised it didn’t come up in my survey. Also doesn’t seem like my PO (who was stickler) to leave a MacGyver job in place. But you never know. Installing a proper vacuum indicator when I’m next back in port.