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Sealant for fuel filler

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Long story (wont bore you with the details) but I need to rebed the new fuel filler (Diesel).

Butyl seems to be a favourite - except for fuel fillers (because it breaks down the butyl when spilt).

Havent foumnd a clear answer on whats best for a fuel filler - Sika or Silicone seem to be an option.....anyone done this before?


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I have never seen a surface mating fuel filter without an o-ring or even heard of using a sealant except in an emergency. 

What do you have exactly? Any photos? 

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This is on the transom. As you can see the neck sits proud of the deck - ordinarily this would be a pain, but because of the placement of it, it will never cause a trip hazard. I felt that the proud neck also offers some protection against water ingress - those flush fillers are fine - but you are relying on the rubber ring in the cap to stop water getting in. 

Anyway when I took this one off - there was no gasket (this was a late 80s design and the filler had probably never been off.

Looks like silicone *might* have been what was used and to be fair it had lasted well with no signs of leaking - but wondered what the modern solution is these days.

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Oh filler  .. Fark I read, filter, sorry... 

Nitrile Rubber. Cut it to shape and use leather hole punch for the screw holes. 

I would use butyl tape on the very inside 3mm of the gasket ring as a last defense against water ingress, and use a cut to size nitrile gasket for the rest. 



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