3.0 engine temp never gets over 160 F

[banderberg]

The dashboard gauge never goes over 160 and most of the time sits around 150 F.

Shouldn't the engine run warmer than this?

I have tested the temp sender with an ohm meter, and pulled the thermostat and tested that it opens/closes at 140 F.

Engine is 1990 3.0L serial number 0D389001

Thoughts?

 

[jhamblett]

If the thermostat is full open at 140 it's suppose to be at 140. Your technically running hot

 

[banderberg]

If the thermostat is full open at 140 it's suppose to be at 140. Your technically running hot

The design is that it begins to open at 140 and is fully open at 160, if I remember correctly.

 

[jhamblett]

The design is that it begins to open at 140 and is fully open at 160, if I remember correctly.

So 150 to 160 is perfect

 

[banderberg]

So 150 to 160 is perfect

Hmm I thought it should run warmer than that..

 

[Scott06]

Hmm I thought it should run warmer than that..

No marine engines run cooler than automotive applications. On a 140 thermostat 150 is normal. This helps with mineral deposits from the open cooling system and also at normal car temps in an open (non pressurized) cooling system it keeps cooling water from boiling

 

[Scott Danforth]

Hmm I thought it should run warmer than that..

why would you think that?

 

[Rick Stephens]

Hmm I thought it should run warmer than that..

Gasoline engines run most efficiently at 210ƒ. Unfortunately, Chevy never designed a block to run open cooling system on plain water. Normally a cast iron block is run with glycol water mix in the cooling system under around 14 pounds pressure. This allows 210ƒ temps without creating steam bubbles. When the system is open and at atmospheric pressures and runs plain water, or worse, seawater, any temps above 165ƒ and steam bubbles form on the cooling passages. Heat does not transfer well through bubbles and the motor has hot spots and over heats. Hence 160ƒ max operating temps.

 

[banderberg]

why would you think that?

Good question.. I guess prior experience with auto engines. Oddly the service manual for my engine no where states what its operating temperature is.. or if it does I cannot find it.

 

[Scott06]

Good question.. I guess prior experience with auto engines. Oddly the service manual for my engine no where states what its operating temperature is.. or if it does I cannot find it.

Whose service manual are you using? Get a factory one if you haven't already.

Pay attention to where your temp gauge sits now - as the impeller in the drive ages you will see the idle temp creep up, or at lest I did on my 3.0. Bottom line get used to knowing where they should be

 

[banderberg]

Whose service manual are you using? Get a factory one if you haven't already.

Pay attention to where your temp gauge sits now - as the impeller in the drive ages you will see the idle temp creep up, or at lest I did on my 3.0. Bottom line get used to knowing where they should be

I have service manual #13 from Mercruiser.

Thanks for the tip.

 

[Scott Danforth]

Good question.. I guess prior experience with auto engines. Oddly the service manual for my engine no where states what its operating temperature is.. or if it does I cannot find it.

automotive engines need to run at higher temperatures for emissions reasons as well as other reasons.

boat motors need to run as cool as possible to keep the minerals in the water from falling out of suspension while being just warm enough to minimize wear. unless you add a heat exchanger to the motor where you can go up a smidge in temp. they also can not have any surface over 200F so they dont burn up your fiberglass boat

raw water cooled motor with carburetor. normally a 140F thermostat
raw water cooled motor with EFI. normally a 160F thermostat
Heat exchanged cooled motor with carburetor, normally a 160F thermostat
Heat exchanged cooled motor with EFI. normally a 180F thermostat

as compared to a car with a pressurized cooling sytem, where your temps are closer to 200F to 230F

 

[jimmbo]

Good question.. I guess prior experience with auto engines. ...

That is where a lot of People get things Wrong. These Engines are operating in Marine Application, which is far different than operating in an Auto/Truck.
While the Coolant Temps are lower in a Marine Engine, I wouldn't be surprised to find that the Piston Temps are higher than in an Auto/Truck. A Truck/Car towing a House Trailer uphill indefinitely at 80mph, might be facing similar loads and internal Temps to a engine in a boat going 35-40 mph