New thermostats are 140 degree VS 160 Degree

[ardeprint]

After doing some research I decided I need to replace my thermostats, even if its not the cause to an overheating while at idle problem. The new thermostats are 140 degree and my originals are 160 degree. My engines normally run at 170 - 180 on the gauges. The place where I bought them insist the 140 degree are the right ones. Mind you I live in South Florida where the water temp is usually high and perhaps having the cooling system open up at 140 could be a benefit.

Are the 140 thermostats OK?

 

[Stray Cat]

My raw water cooled (fresh water cooled) 350 Mags are 160 degrees, I replaced mine last season with Quicksilver part number 807252T 2 (160 degree T stat)

 

[OldSkool]

Most engines are made to operate at 160-190 range. Anything lower than that and the engine does not build enough heat to evaporate any water in the oil or promote good combustion. The best combustion is cool fuel entering a hot (Normal operating temp) engine. Acid levels can increase in the engine oil as the unburnt fuel and carbon build up in the oil.

Unless you're running a modified engine that needs the extra cooling capacity I would leave it as is. If you are having overheating issues then there may be another issue with the engine or ventilation to the engine.

IMHO.

 

[ardeprint]

My raw water cooled (fresh water cooled) 350 Mags are 160 degrees, I replaced mine last season with Quicksilver part number 807252T 2 (160 degree T stat)

Thanks Jeff,
Did that part number come with the needed garkets?

 

[Stray Cat]

No, the gaskets are seperate...sorry I don't have the part number handy for them....my gaskets have a brass eyelet that grounds the housing for the temperature sending unit. Not certain if yours is the same, but suspect that it is.

 

[ardeprint]

No worries I have the PN for the gaskets. I was not sure if I needed to order them separate or they came in a kit. Thanks!!!

 

[CV-23]

I read somewhere that salt water engines have to run at 145 degrees or the salt will crystalize and build up inside the engine block and exhaust. The merCruiser manual calls for a 140 themostat for the 454 and 502 motors. My 454 has a 160 in it and it wants to overheat on the gardenhose muffs....cools fine at 165 in fresh open water. The 160 may make my hotwater heater core work better but I don't really need that hot of water. I'm dropping mine back to 145 for this summer to see if it eliminates the hose problem. My 350 runs fine at 145 in my CV-23, Mike.

 

[northern]

I had mine changed to 160 by a mechanic who did not read the specs. Both engines over heated to 200. I put in the 140s and all is well. I to also was told the low temp is to keep salt from forming in the engines.

 

[Presentation]

Do you have the serial number of your engine? This can be found on the engine cover.

Once you have it please go to this Mercury Marine owned website and see what Mercury says is the correct part: http://www.mercurypartsexpress.com/us/

Once you have the correct part number feel free to shop around. You do not need to buy it from this website, simply use it as a reference tool.

 

[ardeprint]

Do you have the serial number of your engine? This can be found on the engine cover.

Once you have it please go to this Mercury Marine owned website and see what Mercury says is the correct part: http://www.mercurypartsexpress.com/us/

Once you have the correct part number feel free to shop around. You do not need to buy it from this website, simply use it as a reference tool.

Oh I know the part I need. The problem is that the person who sold me the replacement insisted that he was selling me the correct one (140 Degree). Mind you the difference between part numbers is only on the last two digits.
I already went back and insisted they give me the correct one (160).

 

[Ka1oxd]

I actually have the Mercruiser manual for the 1988 engines. All engines they recommend 143 degree. That includes the 454. One other thing that I remember reading is a simple visual review of your gauges. What is the temperature reading when the needle is at the 12:00 position? Most gauges are set so that a quick glance all gauges should be at the 12:00 for proper operation. here is a link dealing with cars, but I remember reading this somewhere for marine application as well. http://brokensecrets.com/2010/08/02/warning-gauges-are-usually-center-normal/ This makes it a quick visual look to see if anything is out of place. In the last 4 boats this has been true and is true with my vehicles. And this has saved me repair costs since I constantly scan the gauges and will take action or inspect more when they are not at the 12:00

 

[CV-23]

Just checked my serial number on the 454.....calls for a 143 thermostat, Mike.

 

[magster65]

I read somewhere that salt water engines have to run at 145 degrees or the salt will crystalize and build up inside the engine block and exhaust. The merCruiser manual calls for a 140 themostat for the 454 and 502 motors. My 454 has a 160 in it and it wants to overheat on the gardenhose muffs....cools fine at 165 in fresh open water. The 160 may make my hotwater heater core work better but I don't really need that hot of water. I'm dropping mine back to 145 for this summer to see if it eliminates the hose problem. My 350 runs fine at 145 in my CV-23, Mike.

I've run in the salt for almost 30 years. It's true, the hotter temperatures will cause salt crust to build up in the little nooks and crannies in an engine casting. It will cause reduced cooling and eventual 'death corrosion'. Stick to the 145 if it's raw water cooled. If the engine has a closed cooling system then go with the hotter ones. What temperature to run at is up to debate (forever) but I like to run them at the 165 or higher. If the cooling system is in good shape the engine should be able to run at 180 with no problems. A gas engines peak efficiency is up around the 195 mark so the closer you are to that the better.
For your overheating on the muffs... when you put them on do you put a piece of tape over the low water pickup on the front of the drive? If not, try that.

 

[88dancer300]

:smt043So if I'm getting this correct, my 1988 merc. 5.7s with closed cooling systems (550 hrs on the engines) running it in salt water, should be running the 160 degree stat? I must have 140s in there now, I'm running at 145 degrees with a load on them. At idle speeds going up the river, (about 45 minutes) the temp. never gets beyond 130. If the engines will run better and more efficiently at 160, I'll change them out. Thanx.

 

[ardeprint]

I've run in the salt for almost 30 years. It's true, the hotter temperatures will cause salt crust to build up in the little nooks and crannies in an engine casting. It will cause reduced cooling and eventual 'death corrosion'. Stick to the 145 if it's raw water cooled. If the engine has a closed cooling system then go with the hotter ones. What temperature to run at is up to debate (forever) but I like to run them at the 165 or higher. If the cooling system is in good shape the engine should be able to run at 180 with no problems. A gas engines peak efficiency is up around the 195 mark so the closer you are to that the better.
For your overheating on the muffs... when you put them on do you put a piece of tape over the low water pickup on the front of the drive? If not, try that.

Your post is a little contradictory. First you advice to replace with 145 degrees. Then you say you like to run above 165. Moreover you mention peak performance is at 195. With a 140 degree Thermostat you wont be reaching 195 unless your cooling system is not running efficiently.

Maybe I misunderstood you, could you clear up...

 

[Ka1oxd]

Merc calls for 143 degrees raw or cooling system.