In a trim system for an outboard engine system, a thrust receiver abuts against an output rod of a trim cylinder which is fixed to a stern bracket. The thrust receiver includes a thrust receiver body which is fitted in a mounting hole defined in a swivel case. The thrust receiver body is fixed by a nut. A steel ball is rotatably supported at a tip end of the thrust receiver body and rollable on an abutment surface of the output rod. The thrust receiver body includes a mounting shaft portion which has a first tapered surface. The first tapered surface is wedged to a second tapered surface formed in the mounting hole, thereby causing the mounting shaft portion and the mounting hole to smoothly abut against each other. Thus, it is possible to prevent the thrust receiver mounted on the swivel case from chattering relative to the swivel case.