Mercury - Fuel Line Fitting Fuel System Component Brass and Composite 22831T3. Overview. A reliable fuel connection is key to smooth operation on any classic outboard. The Mercury Marine 22831T3 Fuel Line Fitting is designed specifically for Mercury and Mariner TwoStroke outboards built in 1971 and earlier, giving you the same solid, leak-free connection these engines were built around. With its twist-lock design, it attaches quickly and stays secure, keeping fuel flowing evenly and efficiently.