Diesel fuel filter water separator

[Bakoboat]

Can anyone explain the purpose of the large plastic screw on top of my fuel filter/water separator? This is connected to my diesel geny and the screw started leaking when the tanks were filled with diesel. The boat is also sloped forward on dry dock for removal of the shafts. The screw is connected to a brass rod that goes into the filter housing. Last night I opened the screw a few turns and it stopped the leaking, no sign of any seepage when I returned this morning. I have changed the filter and cleaned the bottom bowl. Assuming this is for bleeding or ? How do I adjust this for proper operation.
Thank-you

[Viper]

What filter are we talking about? The primary (remote) like a Racor or the genny on board secondary filter? Either way, it shouldn't leak. That type of setup usually has a gasket or o-ring to seal the fastener.

[Bakoboat]

It's a racor style although I cant see any branding. It's the first in line from fuel tank before entering geny. Picture below.

20230508_123115.jpg

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[Viper]

Looks like a 220R assembly though the white screw is throwing me off as I'm used to seeing black ones. Parker/Racor usually has service kits for their filter assemblies but I have a feeling the 220R is out of production.

https://www.parker.com/static_content/parkerimages/Racor/7238%20Rev%20D%20(200%20Series).pdf

BTW, did you know that there are "Marine Rated" filters for most Racor assemblies now?!

[Bakoboat]

Thanks very much for the help, the link had operating instructions - the white plastic nut is the primer pump, with vent screw open you pump this up and down to bleed the fuel/air out.
Thanks again and yes I read about marine Rated racor products.

[Bakoboat]

After discussing with rep from parker (manufacturer) decided to replace with racor 490 model. Seal kit for the 220 was approx 125 with shipping and taxes, new 490 unit was 220.
Thanks for the help everyone