Generalities: If your engine is bone stock, 260hp small block, 310 hp big block, you probably won’t gain any significant speed. You will benefit from the safety of our manifold (won’t eat your motor when it dies), and light weight; save 70 to 125 pounds over the cast iron stuff. When you step up the performance to the next level, like the 365/385 hp 454 Magnum, or the 385/415 hp 502, for example, the performance gains are significant. We have a boat test elsewhere in the website on a 365 carbureted Magnum Merc in a 22’ Donzi. Hot Boat did a complete test on the boat, including fuel flow and such. After the test, they brought it to the dock and changed the manifolds from the Merc cast iron to our standard Big Block set. No other changes. No prop, no timing, no nothing. Picked up 300 r’s and 6 ½ mph. That is the most optimistic report that we have seen in the 17 years that we have been building this manifold. The least optimistic? “Lost 3 mph!” That is pretty much impossible. Average? Trailer Boat Magazine did a 10 month series on a Sea Ray Pachanga with a 502” Crusader. At the end of the article, they took off the Crusader manifold set and installed our Bravo length set. Picked up 225 rpm’s and 4.5 mph. The headline for that episode is “Of all the changes that we made over the months, the Stainless Marine manifolds made the biggest improvement”. That increase is typical of the reports that we receive from our customers. The Stainless Marine Hi-Torque exhaust manifold is the most sophisticated on the market. Unlike the run-of-the-mill cast aluminum manifold, the Hi-Torque is a hybrid, utilizing a casting where it is needed, and metal fabrication where desirable. We probably have two or three times the man-hours in each manifold than the cast guys, but it pays off for the boater in the long run. We cast the runner portion of the manifold in A356 aluminum. A356 is best castable alloy in strength vs. corrosion numbers. We then draw form the cooling jackets of 5052 aluminum, zero temper. 5052 is the best alloy of noncorrosive cold-formable aluminum sheet. Five year limited warranty.