What's not obvious about Evinrude E-TEC is what's inside the engine block. Evinrude E-TEC incorporates pistons made from a new alloy, which was developed by NASA. This alloy has proven to be 2 to 3 times stronger at operating temperature than the aluminum alloys pistons are traditionally made with. The pistons used in the 40 through 60 and the 75/90 are what's known as "full-skirt" pistons. The internal design of the block (the intake, exhaust and transfer ports) doesn't require machining "port windows" into the piston. This combined with the new alloy, increase the piston strength and durability.