Also, since the hydrofoil works only if the boat is still on the surface of the water, it prevents the boat from rising out of the water and from causing the boat to. Don’t send that old car to the crusher! recycle it the green way by turning it into a walk-behind farm tractor. these free vintage plans show you how.. How fast does it go? for estimating the speed for small outboard planing boats see planing speed boat chart. this chart should be used for.