Just purchased a 1995 90 Mariner that has been sitting for about two years. I have pulled the carbs and cleaned as per Selco manual. I have put a new switchbox on the engine also. I have good spark at all spark plugs, I have good compression on all three cylinders, and the carbs are clean. I am at a loss, it will not even spit or try to fire. Does anyone have any sugestions???