You did not say what engine you have but if it is a quad 4 you will have two water necks one houses the thermostat the other one does not I think the stat is in the back one.just remove the two or three bolts drain the water down a bit and have a new gasket or blue glue ready to reseal it.be sure the new one goes in like the old came out otherwise it will not heat.do not put it in upside down