Pacific Fiberglass co-located in Canal Boatyard in Ballard is who I'd use for restoration of a Boston Whaler. Yes, they work on a lot of yachts but they love little boats, are fairly priced, and deliver excellent workmanship. I have seen a few Outrage 18 boats in their yard
For an OEM-looking fuel tank cover re-core, Doug and his team are the ones.
They are fiberglass repair only.
CSR should also be on the list of Boston Whaler restoration firms in Seattle. They are my go-to for larger boats and projects. A full service boatyard that can do it all and also delivers excellent workmanship.