Doug Dotson wrote:

I have successfully removed the cleanout ports (3)
from my port fuel tank. Quite a mess in there!
When I put them back in, does anyone have any advice
on what sealant to use? They are submerged in fuel
most of the time.

You can use SikaFlex 291, it is compatible with diesel.

Do not use 3M-5200, SikaFlex 292 or silicone, none of which are
compatible with diesel.

HTH

Lew