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Many dealers and some owners drilled a 1" hole aft of the gas tanks mats for the fuel line when a single large 20-24 gallon fuel tank was installed.

While a trim ring would be improve appearance, it is wise to add marine sealant to the hole to seal the fiberglass and any embedded wood that may be exposed.

Boat life of similar polysulfide caulk is good. I might try using a narrow paint brush to lather up the sides.

Your local hardware store may have a plastic grommet that can be added to give it a finished look. Something like this (without cover)
[url]https://www.amazon.com/MyCableMart-White-Management-Grommet-Removable/dp/B06XCJRG5B?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duckduckgo-osx-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B06XCJRG5B
[/url]

To save reinstalling the fuel line, cut the grommet horizontally and slip it over the existing line and down into place.