Re: 40hp johnson year
Unfortunately, the gasket is listed as NLA. You have two options:
1, Find a rubber fuel line that is the appropriate size, and slit it so it fits over the flange on the bottom cover. Perhaps secure with some 3m weatherstripping adhesive.
2. Order some of the vintage gasket seal from nymarine.ca (look in the "Parts for Sale" section. Secure with 3m weatherstripping adhesive.
I hope that helps!