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#1
posted to rec.boats.building
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Can cooling water be to cold on a Mercruiser
wrote in message ups.com... I am buying a used boat from Stony Point, NY. It has a Mercruiser V8 5.0 with 190 HP with 300 hours on it. I live in Greenland. An island in the arctic region east of Canada where the seawater temperature is around 36-37 F degrees. And thatīs where there might be a problem. I am told that the motor is "use" to be cooled of with warmer water temps around the more southern part of the world. And when I get the boat and the motor is cooled down with seawater that is 36-37 F degrees then it migth not run smooth anymore or develop somekinda problem. Is this story a myth or is there something to it? And if the story is right how can i prevent any problem with the motor. I cannot install fresh water cooling system as it is too late for this motor because it has already 300 hours of seawater cooling I am told. Any help or suggestions will be much appreciated. Sal****er cooling is 'uncontrolled' water circulation drawn from under the boat- with very little control of the engine operating temperature. If you are concerned about 'stabilizing' the engine temperature, the only way to do it is by freshwater cooling. This will allow the engine to run at operating temperature (controlled by the thermostat) and at least run more efficient. And it is NOT too late to do this. |
#2
posted to rec.boats.building
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Can cooling water be to cold on a Mercruiser
Just to amplify the following advice a bit, engines run most efficiently
when HOT! The only reason your auto engine doesn't run a lot hotter is that it's too hard to keep the pressure reasonable when you go much above 212 F. The other potential problem is "shock cooling." Idle a bit and then turn the engine off. Heat will percolate out from the exhaust and from the combustion chambers. When it's started again, the cold water will cause different parts of the engine to shrink at different rates and you can get piston scuffing at least and possibly other dire actions. That said, there isn't that much difference between the Caribbean's 85 degree water and your 37 degrees. The effects are calculated on the "absolute" temperature scale, so it's 545 to 497 (10%) on the Rankine scale. Roger http://home.insightbb.com/~derbyrm "theMooseisLoose" wrote in message news:8kuKf.34509$6f2.19385@trnddc02... wrote in message ups.com... I am buying a used boat from Stony Point, NY. It has a Mercruiser V8 5.0 with 190 HP with 300 hours on it. I live in Greenland. An island in the arctic region east of Canada where the seawater temperature is around 36-37 F degrees. And thatīs where there might be a problem. I am told that the motor is "use" to be cooled of with warmer water temps around the more southern part of the world. And when I get the boat and the motor is cooled down with seawater that is 36-37 F degrees then it migth not run smooth anymore or develop somekinda problem. Is this story a myth or is there something to it? And if the story is right how can i prevent any problem with the motor. I cannot install fresh water cooling system as it is too late for this motor because it has already 300 hours of seawater cooling I am told. Any help or suggestions will be much appreciated. Sal****er cooling is 'uncontrolled' water circulation drawn from under the boat- with very little control of the engine operating temperature. If you are concerned about 'stabilizing' the engine temperature, the only way to do it is by freshwater cooling. This will allow the engine to run at operating temperature (controlled by the thermostat) and at least run more efficient. And it is NOT too late to do this. |
#3
posted to rec.boats.building
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Can cooling water be to cold on a Mercruiser
Re the difference - it's significant.
This is a heat transfer / cooling issue, not one where you can apply the ideal gas laws and use Rankine or absolute temperatures. If the engine block is at say 250F, the rate of cooling for 37 F coolant vs 85 F is (250 - 37) / ( 250 - 85). More importantly, if temperature difference required to remove the developed heat is say 100F, it will run at 185F in the Caribbean and 137 in the colder water ... You can't just restrict the flow or the temperature becomes uneven. So you need a circulating system - might as well consider a fresh water one .. David "derbyrm" wrote in message news:xBuKf.788735$_o.605338@attbi_s71... Just to amplify the following advice a bit, engines run most efficiently when HOT! The only reason your auto engine doesn't run a lot hotter is that it's too hard to keep the pressure reasonable when you go much above 212 F. The other potential problem is "shock cooling." Idle a bit and then turn the engine off. Heat will percolate out from the exhaust and from the combustion chambers. When it's started again, the cold water will cause different parts of the engine to shrink at different rates and you can get piston scuffing at least and possibly other dire actions. That said, there isn't that much difference between the Caribbean's 85 degree water and your 37 degrees. The effects are calculated on the "absolute" temperature scale, so it's 545 to 497 (10%) on the Rankine scale. Roger http://home.insightbb.com/~derbyrm "theMooseisLoose" wrote in message news:8kuKf.34509$6f2.19385@trnddc02... wrote in message ups.com... I am buying a used boat from Stony Point, NY. It has a Mercruiser V8 5.0 with 190 HP with 300 hours on it. I live in Greenland. An island in the arctic region east of Canada where the seawater temperature is around 36-37 F degrees. And thatīs where there might be a problem. I am told that the motor is "use" to be cooled of with warmer water temps around the more southern part of the world. And when I get the boat and the motor is cooled down with seawater that is 36-37 F degrees then it migth not run smooth anymore or develop somekinda problem. Is this story a myth or is there something to it? And if the story is right how can i prevent any problem with the motor. I cannot install fresh water cooling system as it is too late for this motor because it has already 300 hours of seawater cooling I am told. Any help or suggestions will be much appreciated. Sal****er cooling is 'uncontrolled' water circulation drawn from under the boat- with very little control of the engine operating temperature. If you are concerned about 'stabilizing' the engine temperature, the only way to do it is by freshwater cooling. This will allow the engine to run at operating temperature (controlled by the thermostat) and at least run more efficient. And it is NOT too late to do this. |
#4
posted to rec.boats.building
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Can cooling water be to cold on a Mercruiser
Good answer. I was wondering about the same issues. Not to throw dirt at
anything because I love the motor, I have heard through the grapevine that the Mercruisers "like to be dry" ...rust easily. At this point, that's only a rumor, but the point is that a nice salt-free freshwater system and good ventilation would be good for the motor (any motor, really.) Brian D "David Flew" wrote in message ... Re the difference - it's significant. This is a heat transfer / cooling issue, not one where you can apply the ideal gas laws and use Rankine or absolute temperatures. If the engine block is at say 250F, the rate of cooling for 37 F coolant vs 85 F is (250 - 37) / ( 250 - 85). More importantly, if temperature difference required to remove the developed heat is say 100F, it will run at 185F in the Caribbean and 137 in the colder water ... You can't just restrict the flow or the temperature becomes uneven. So you need a circulating system - might as well consider a fresh water one .. David "derbyrm" wrote in message news:xBuKf.788735$_o.605338@attbi_s71... Just to amplify the following advice a bit, engines run most efficiently when HOT! The only reason your auto engine doesn't run a lot hotter is that it's too hard to keep the pressure reasonable when you go much above 212 F. The other potential problem is "shock cooling." Idle a bit and then turn the engine off. Heat will percolate out from the exhaust and from the combustion chambers. When it's started again, the cold water will cause different parts of the engine to shrink at different rates and you can get piston scuffing at least and possibly other dire actions. That said, there isn't that much difference between the Caribbean's 85 degree water and your 37 degrees. The effects are calculated on the "absolute" temperature scale, so it's 545 to 497 (10%) on the Rankine scale. Roger http://home.insightbb.com/~derbyrm "theMooseisLoose" wrote in message news:8kuKf.34509$6f2.19385@trnddc02... wrote in message ups.com... I am buying a used boat from Stony Point, NY. It has a Mercruiser V8 5.0 with 190 HP with 300 hours on it. I live in Greenland. An island in the arctic region east of Canada where the seawater temperature is around 36-37 F degrees. And thatīs where there might be a problem. I am told that the motor is "use" to be cooled of with warmer water temps around the more southern part of the world. And when I get the boat and the motor is cooled down with seawater that is 36-37 F degrees then it migth not run smooth anymore or develop somekinda problem. Is this story a myth or is there something to it? And if the story is right how can i prevent any problem with the motor. I cannot install fresh water cooling system as it is too late for this motor because it has already 300 hours of seawater cooling I am told. Any help or suggestions will be much appreciated. Sal****er cooling is 'uncontrolled' water circulation drawn from under the boat- with very little control of the engine operating temperature. If you are concerned about 'stabilizing' the engine temperature, the only way to do it is by freshwater cooling. This will allow the engine to run at operating temperature (controlled by the thermostat) and at least run more efficient. And it is NOT too late to do this. |
#5
posted to rec.boats.building
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Can cooling water be to cold on a Mercruiser
You're right regarding the cooling capacity. I was addressing the size
changes of the metal parts. Roger http://home.insightbb.com/~derbyrm "David Flew" wrote in message ... Re the difference - it's significant. This is a heat transfer / cooling issue, not one where you can apply the ideal gas laws and use Rankine or absolute temperatures. If the engine block is at say 250F, the rate of cooling for 37 F coolant vs 85 F is (250 - 37) / ( 250 - 85). More importantly, if temperature difference required to remove the developed heat is say 100F, it will run at 185F in the Caribbean and 137 in the colder water ... You can't just restrict the flow or the temperature becomes uneven. So you need a circulating system - might as well consider a fresh water one .. David "derbyrm" wrote in message news:xBuKf.788735$_o.605338@attbi_s71... Just to amplify the following advice a bit, engines run most efficiently when HOT! The only reason your auto engine doesn't run a lot hotter is that it's too hard to keep the pressure reasonable when you go much above 212 F. The other potential problem is "shock cooling." Idle a bit and then turn the engine off. Heat will percolate out from the exhaust and from the combustion chambers. When it's started again, the cold water will cause different parts of the engine to shrink at different rates and you can get piston scuffing at least and possibly other dire actions. That said, there isn't that much difference between the Caribbean's 85 degree water and your 37 degrees. The effects are calculated on the "absolute" temperature scale, so it's 545 to 497 (10%) on the Rankine scale. Roger http://home.insightbb.com/~derbyrm "theMooseisLoose" wrote in message news:8kuKf.34509$6f2.19385@trnddc02... wrote in message ups.com... I am buying a used boat from Stony Point, NY. It has a Mercruiser V8 5.0 with 190 HP with 300 hours on it. I live in Greenland. An island in the arctic region east of Canada where the seawater temperature is around 36-37 F degrees. And thatīs where there might be a problem. I am told that the motor is "use" to be cooled of with warmer water temps around the more southern part of the world. And when I get the boat and the motor is cooled down with seawater that is 36-37 F degrees then it migth not run smooth anymore or develop somekinda problem. Is this story a myth or is there something to it? And if the story is right how can i prevent any problem with the motor. I cannot install fresh water cooling system as it is too late for this motor because it has already 300 hours of seawater cooling I am told. Any help or suggestions will be much appreciated. Sal****er cooling is 'uncontrolled' water circulation drawn from under the boat- with very little control of the engine operating temperature. If you are concerned about 'stabilizing' the engine temperature, the only way to do it is by freshwater cooling. This will allow the engine to run at operating temperature (controlled by the thermostat) and at least run more efficient. And it is NOT too late to do this. |
#6
posted to rec.boats.building
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Can cooling water be to cold on a Mercruiser
way's why the Mercruiser and all the other I/O systems that use automotive
engines( that I know of) do have a circulating system, same as you car.,and raw water flow isn't restricted by the thermostat on the inlet. They actually have been engineered to account for your concerns and ,amazingly they do work, with or with out "closed loop" exchanger system. The decision weather to use closed loop fresh water system is more often a practical one, if the engine is dificult (expensive)to remove or not is a big consideration (plus freezing concerns). The point being, why spend something like 500-1000 bucks for the exchanger system to protect a cheap car engine? The cooling system corrosion issues won't make the engine last forever anyway? That is unless you engine is buried deep under some nice stuff rather than being under a lift up engine cover as most of these setups are. To an extent you could think of these ase thowaway engines. They are relatively un-expensive and have limited useful life. Oh, but their cooling systems do work! -- Ron White my boatbuilding web site is: www.concentric.net/~knotreel |
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