86 mariner 75hp 4cyl. runs goods, but been sitting for about 6yrs. wanted to spray some product down the carbs (2). dont have a "local" boat shop so i went to auto parts store and bought marvel mystery oil to mix with gas for carbon... also bought a gunk carb cleaning spray. the only question i have is that when i spray it in the upper carb.. it will idle down which is normal because of the cleaning product, but when i spray bursts into the lower carb it will idle up... why would one carb idle down and almost stall when spraying bursts but why would the other carb idle up while spraying?