Water bypass fittings increase engine performance and improve cooling by diverting some of the water from the cylinder head to the bypass fitting and overboard. Performance is gained by reducing the amount of water forced into the exhaust system allowing the engine to produce more power because of the reduction in expanding gases in the exhaust pipe. This has been done for years and is an accepted technique to gain added acceleration with a low buck approach. These billet machined bypasses are designed for the larger watercraft engines and for expert tuners who know exactly what they want. They're precision machined, polished, and anodized to a beautiful and long lasting finish.