Sold on an exchange basis - A rebuildable core exchange is required.SBT's Short Blocks are ready to install, just bolt on your head and the rest of your externals. The shortblock is an assembled lower unit that comes with the head and valve cover gaskets.Engine installation kit is optional.Please note - These short blocks will work for the 2002-2005 Sea-Doo 4-Tecs with the additional purchase of an SBT Rocker Arm Shaft: 46-112-69.