Parts Shop

Thermostats and Poppet Valves

 

Thermostats and poppet vales, or pressure release valves are both parts of your cooling system.  Thermostats are designed to regulate the flow of water through your cylinder head.  As the engine gets hotter the thermosats open up allowing more water to flow.  When the engine is cooler the thermostats close to allow less water to flow so your engine operates at the correct temperature.  Poppet valves or pressure release valves allow pressure to release from your cooling system. 

 

A  poppet valve is sort of a water-pressure regulator for the cooling system on an outboard engine. At slow rpm's the pressure from the water pump is pretty low, so the poppit stays closed, and allows all the cooling water from the impeller to circulate thru the engine cooling system. At high rpm, the water pump volume & pressure is much higher. The poppit opens at a pre-determined pressure and allows the "excess" water to bypass the cooling system.

 

Both thermostats and Poppet valves need to be inspected yearly.  Here is an easy way to check your thermostats:

 

Thermostat Test Procedure

Begin heating a pot of water on a stove. Suspend the thermostat along with a thermometer in the slowly heating water with a string (do not allow the thermostat or thermometer to touch the bottom or sides). The thermostat should begin to open at the temperature that is marked on it and should be fully open at 20 degrees F higher. Allow the water to cool, the thermostat should be fully closed no later than 10 degrees F below the temperature marked on it. If the thermostat does not meet these specs, replace.