New Old Stock 25XS Exchange Kit. Mercury Part No. 872-9533A 8. This kit contains a new block, crankcase, port covers, exhust cover, gaskets, pistons, with rings and pins, bearings, miscellaeous hardware including the instructions. The price we have listed is what Mercury was selling the Kit for in 1999. Shipping charges will depend on destination, we only charges what it costs us to ship the item.