These replace your Mercury 2-stroke outboard thermostats with new seals and restrictor washers to regulate water pressure and flow for high-performance racing and river running.
 
Includes two (2) Thermostat Seals with Stainless Washers.
 
Options:
1) 3/32" ID washers (small) for more/higher water pressure
2) 1/8" ID washers (medium) for medium water pressure