Abstract: A jet-propelled boat having an inboard motor and a hull which incorporates an inlet ramp penetrated by a driven shaft. The driven shaft couples a drive shaft of the inboard motor to an impeller of a water jet propulsion assembly which is mounted in cantilever fashion to the hull transom. The hull penetration is accomplished by a through-hull housing which is installed in an opening formed in the hull inlet ramp. Preferably the through-hull housing is made of thick metal plate with a transverse linear bore for shaft penetration and a peripheral flange which seats in a peripheral recess formed along the edge of the opening in the inlet ramp. The through-hull housing is clamped to the recessed hull edge, which forms the opening in the inlet ramp, by an annular clamp plate. An inlet grate extending from the outboard surface of the through-hull housing. A through-hull housing and inlet grate assembly is installed in the hull opening as a module.