Being a 4 branch design they increase the power / efficiency of the engine between 6 - 10% meaning better fuel economy at cruising speeds. Thanks to their increased efficiency and huge weight saving, all the time you are enjoying your boating you are actually getting back your initial outlay on them. It has been calculated that depending on boat type, the fuel saving at normal cruising speed should pay for them at 175 / 200 hrs running time and even less if fitted to a Swaymar engine.