I have five old cars and a 24 ft boat. I put non ethanol in the prewar cars and boat. During the winter I use Sta-bil products. Everything starts right back up in the Spring.
I have used Seafoam in the past mainly to clean out carbon deposits and moisture when I first buy an old car.
For two years, thanks to Covid, we didn’t run the boat. I really thought the gas would be bad and the fuel injectors would have to be replaced. Thanks to Sta-bil Marine it started right up and ran fine.