Two thumbs up for Seafoam. I add the Seafoam, then run the engine until it's up to temp, then top off the tank. The reason for running the engine is to get the stabilizer into the fuel pump and carburetor. In the Spring I fill up the boat after every trip. Later in the year I may go two or three trips before fueling. After a long lay up, all the fresh fuel you can add, just can't hurt.