Fuel tank

[Klausen]

Hello,
my name is Klaus and my ship is a 37cr/2006. Sorry for my poor english. Hope that anyone can help! On the top of my fuel tank are 3 hoses attached, fuel out and return and heating. A fourth hole is sealed with a dummy plug. What size of thread may it have? I want to install an inspectionpipe through this hole.
Thanks a lot for answering
Klaus

[Odysseus]

Hi Kausen, I have used these holes for an inspection pipe in bottom of tank, there is a artical about my fitting on this forum you can serch for it. photo attached.

The grommets are available still but info is at home, let me know if you want it.

Odysseus
Bav 38

[Klausen]

Hi, Odysseus!
I think the metal dummy plug is screwed in, but if any grommet will fit, let me know.
Thanks
Klaus