The watercraft ramp comprises a frame and a plurality of hull-support assemblies mounted thereon. The frame has a pair of elongated channel rails held in laterally spaced condition. Each rail has a longitudinally aligned internal recess and a longitudinally aligned elongated slot for access into the internal recess. The slot is narrower than the transverse width of the recess. Each hull-support assembly has a mounting bracket, a fastener for fixing the bracket on a rail, and at least one hull roller. The fastener has a locking part that extends through the rail slot into the internal rail recess for locking engagement to the rail at any desired location. A stabilizer part on the bracket cooperatives with the slot to maintain alignment of the bracket on the rail.