Technical Information - Fresh Water Cooling Systems

Our General Manual

What Fresh Water Cooling is ------ 
 
"Fresh Water" cooling (also known as "Closed Cooling") is the marine version of the cooling system that you have in your car.   Most marine engines started out as a non-marine engine and were then designed to have a clean non-corrosive antifreeze coolant circulating between the engine and a "radiator". Normally air passes through the radiator and cools the engine coolant but in the marine version of this cooling system (fresh water cooling), the radiator is replaced with a "liquid to liquid" heat exchanger. Instead of air, sea water passes through one side of the heat exchanger and absorbs the heat from the engine coolant and is expelled out of the boat through the exhaust. On the other side of the heat exchanger the engine coolant is then circulated back into the engine.    Many marine engines use the initially less expensive, "Raw Water" cooling system rather than "Fresh Water" Cooling.  In this case, polluted corrosive seawater is pumped directly into the engine.  The "Raw Water" eats away at the very base metal of a marine engine causing permanent damage. 
 

The difference between a full and half system kit ------ 
 
 With a HALF System (Block Only), the treated fresh water is circulated through the engine block, thermostat, expansion tank, heat exchanger and circulation pump. It is not routed through the exhaust manifolds. "Raw Water" which has removed heat from the engine through the heat exchanger is then injected into the exhaust manifold, from which it flows to the exhaust elbow to cool and exit through the exhaust.  The half system does not provide the same degree of protection for your engine as a FULL (Block and Exhaust Manifold) closed cooling system, but is generally easier to install, less expensive, and may be the only option available if your engine's pump capacity, electronic control system, or other factors prevent a FULL system from being safely installed on a particular engine or boat.
   
In a FULL System (Block and Exhaust Manifolds), all parts of the engine are cooled with circulated antifreeze. "Raw Water" which has removed heat from the engine through the heat exchanger is then injected into the exhaust elbow and exits through the engine exhaust.  The full system provides the maximum protection to your engine from the ill effects of direct "Raw Water" cooling. 
 
 
The difference between premium kits and standard kits ------ 

One difference is that the premium kits are powder coated and the standard kits are painted in primer only.   Standard kits use standard factory fittings and standard end covers. The premium kits use heavy duty cast end covers and in full systems will replace the 1" hose to 3/4" NPT fittings in the bottom of the exhaust manifolds with hi-flow fittings to achieve higher flow rates.   Another difference between premium kits and standard kits is where the thermostat is located.   On a standard kit the thermostat is in the standard location and has a fixed or (static) by-pass and on the premium kits have a built in high flow controlled by-pass thermostat that insures proper flow of water through the heat exchanger and the engine at all times, with water by-passing the heat exchanger at start-up, when the thermostat is closed, to get the engine up to operating temperature quicker and closing off the by-pass once operating temperature is reached and thermostat opens. This guarantees full flow through all temperature ranges.   This is called a thermostat-controlled by-pass.