Sierra 18-3619 Thermostat Kit - Fresh Water CooledSierra replacement fresh water cooled thermostat kit. This kit has a temperature rating of 150F (66C) and includes a thermostat housing gasket. Fresh Water (Closed) Cooling System; 4.3, 5.0, 5.7 (all models) 1993-Current / 5.8 (all models) 1993-1996; 7.4 (all models) 1991-2000 / 8.1 (all models) 2000-Current / 8.2 (all models) 1993-200;