I have already winterized my boat and forgot the Sea Foam. Can I still add it without running the engine? [SOLVED]

Thanks for the question, Christine!

Yes, you can still add Sea Foam. It will still stabilize and protect the fuel in the fuel tank. Add a minimum of 1 oz per gallon of fuel in the tank. Adding a whole can works too if you want to go the simple route. Adding more than 1 oz per gallon is fine and will do a good job cleaning up any fuel residues when you run it in the spring.