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ROB
05-06-2009, 11:24 PM
I've read many of the thermostat threads and I think I have my own question answered, but... The other day I changed out my impeller on my '89 240 Maristar. At the same time I decided to take a look at my thermostat and decided to change it as well. Purchased a 180 instead of 143 or 160. For the heck of it, I ran the boat on the fake a lake for about twenty minutes. She got up to about 180 to 185. It was about 85 out that day in beautiful Souther California. Do I change the thermostat now or take her out to see how she performs in the water. Yes, I now know, normal operating temp should be between 140 and 180. Go ahead, let me have it.

ProStar Slalom
05-06-2009, 11:37 PM
I'm no pro, but I wouldn't recommend leaving a 180 in it. Water boils at 212....doesn't leave you a whole lot of room to play with. On my '87 I replaced the 143 with a 160, and for me, even the 160 allowed it to get hotter than I was comfortable with, so I went back to the 143. You're probably fine with either 143 or 160, but get rid of the 180.

CantRepeat
05-07-2009, 04:22 AM
Motors have thermostats for a reason. One of those reasons is the engine was designed to run at a set temperature and changing that isn't normally a good idea.

Jesus_Freak
05-07-2009, 01:22 PM
I'm no pro, but I wouldn't recommend leaving a 180 in it. Water boils at 212....doesn't leave you a whole lot of room to play with. On my '87 I replaced the 143 with a 160, and for me, even the 160 allowed it to get hotter than I was comfortable with, so I went back to the 143. You're probably fine with either 143 or 160, but get rid of the 180.

Few comments:

1. Water boils at 212F at sea level. Pressure varies inside your engine. At the water pump discharge it is higher (higher BP). At the water pump suction it is lower (lower BP). At the same time, running at higher altitudes increases the risk of boiling.

2. Even if the gauge shows 185F, you can be assured that some spots are higher than that, depending on your load/speed. Combine this with number 1.

3. The manufacturer, albeit not perfect, decides on a thermostat setting considering many factors. I would not question that.

Switch it out! :)

CPlane Pilot
05-07-2009, 02:09 PM
Let it be known that Im far from an engine guru. However, let me throw in this perspective. Your engine will develop condensation internally that will collect in the oil. Obviously you want to burn off that condensation. This is done by getting the oil temp up to a sufficient level. I would think that a water temp of 180 helps the engine with plenty of cushion before overheat.

Again, the manufacturer recommends a correct thermostat for a reason and I wont question that logic. Im just opening this question up to criticism.

tocoldtorace
05-07-2009, 02:59 PM
so what is the prescribed thermostat. i have a 93 prostar and last year i changed out my thermostat and put a 180 in it and it seems to run fine. water temp never above 185 or so.

Sodar
05-07-2009, 03:06 PM
I believe all engines beside the LT-1's should have a 160.

LT-1's should have the 143 because of the aluminum heads.

Also, ROB... since you are in SoCal, I am not sure, if you run in salt or not, but I have heard that you want to step it down cooler than 160 because the salt will crystalize at about 160.

ROB
05-07-2009, 10:44 PM
I never run in salt nor in brackish water, but I'm thinking on those hot days on Powell, Mead, or just on some of the local lakes, I might want the extra cushion that I will get from the 160. I was just curious to see if anyone else had run a 180 with success. Thanks.

Jesus_Freak
05-08-2009, 01:32 PM
Let it be known that Im far from an engine guru. However, let me throw in this perspective. Your engine will develop condensation internally that will collect in the oil. Obviously you want to burn off that condensation. This is done by getting the oil temp up to a sufficient level. I would think that a water temp of 180 helps the engine with plenty of cushion before overheat.

Again, the manufacturer recommends a correct thermostat for a reason and I wont question that logic. Im just opening this question up to criticism.

Yes, good point. This, along with increased thermal (Carnot) efficiency, increased solubility of contaminants in oil, etc. drive the desired temperature setpoint higher. I guess the final decision is one of trade-offs.

Chicago190
05-08-2009, 02:02 PM
Yes, good point. This, along with increased thermal (Carnot) efficiency, increased solubility of contaminants in oil, etc. drive the desired temperature setpoint higher. I guess the final decision is one of trade-offs.

On the flip side, hotter engine --> hotter air intake temperatures --> less dense air --> decreased engine performance.

160 is recommended, except in the LT1 which has both 143 and 160 degree thermostats.

Jesus_Freak
05-08-2009, 03:02 PM
On the flip side, hotter engine --> hotter air intake temperatures --> less dense air --> decreased engine performance.

160 is recommended, except in the LT1 which has both 143 and 160 degree thermostats.

Yes, and on the flip-flip side, hotter engine --> hotter air intake temperatures --> higher reaction temperatures --> increased engine performance* when operating below WOT 8p

* Assumes one does not have a detonation problem, nor does one care about nitrogen-oxide derivative emissions.