Permatrim Hydrofoil PlatePermatrim is our preferred brand of hydrofoils for outboard motors. Hydrofoils are a good solution for most cavitation and ventilation issues. Both are issues that are common with light weight, catamaran style boats. You should only need a permatrim plate if you are using an outboard that is 10HP or above. They are also useful for lower HP outboards to help get the boat up on a plane.