Mercruiser 470 cooling modification

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  #1  
Old 05-11-06, 07:34 PM
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Lightbulb Mercruiser 470 cooling modification

I am getting ready to buy a boat powered by a mercruiser 470. As of now it is a very clean and good running engine but I am unsure of one issue. The previous owner modified the cooling system to get rid of the heat exchanger. He has both water pumps running in the same direction and the two seperate parts of the cooling system run together in a way that allows the engine to circulate lake water. So instead of the lakewater cooling the engines coolant in the heat exchanger, lakewater is pumped through the engine and back out. He ran it this way for a summer and has had no problems. I am unsure of wheather to be weary of this setup or not. I don't understand how the engine can maintain a constant temp if every time the thermostat opens it draws in cool lakewater. However, i am not familiar with this engine or it's cooling system. Anyone know if this is an ok setup?
 
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  #2  
Old 05-25-06, 07:01 AM
Pwrbait
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Defineatly NOT ok for this. Engines are designed to run in a specific temperature range for maximum efficiency, and a heat exchanger is essentally a radiator to keep that engine where it's designed to be. When you say both water pumps, I assume you mean the external raw water pump and the engines water pump. They will turn the same directuion because of engine rotation. The problem with what this guy has done, is the r/w is not given a chance to remove the heat from the jacket water before it's pumped over board. That is what the heat exchanger is designed to do. It's filled with r/w, the jacket water enters the tubes for the h/e, and the surrounding r/w removes the heat and is pumped o/b. By removing the h/e, the constant flow is not removing the heat efficiently enough. Over extended running times, this will only cause problems. I'd stay far far away from this boat, not only for the h/e reason, but if he's done that...what else has he done??
Hope this helps
Chris
 
  #3  
Old 05-29-06, 12:06 PM
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Angry Mercruiser 470 cooling modification

More than not OK. The 470 has an aluminum block and a cast iron head. Not rumming a 50/50 antifreeze/water mixture will cause severe corrosion in the engine do to dissimilar metals, ruining the engine. This is the reason Mercury used a closed cooling system. One season in fresh water may not have harmed it too much, depending on how much it was run but probably would have been a killer in salt water. If you replace the heat exchanger, be sure to use the 4" one and not the 3".
 
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