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.Timing Chain, Chain Guide and Tensioner Assesmbly.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.This replaces the check valve function in the 2002-2005 cases.Engine installation kit is optional.