AQ131 Twin Temp problems

Hi -=
I have twin AQ131s. The

Hi -=
I have twin AQ131s. The temp on one motor never goes above 150 and the other stays around 200 with redline over 20Krpm & on plane. A few questions: Is there a way to test the temp guages to see if they are acurate?
I assume that one or both motors may need new thermostats? I have the Seloc maual but it doesn't show the actual location of the thermostat - can you help?
Any other advice for trouble shooting?

"Gary,

Regarding the motor

"Gary,

Regarding the motor that goes over 200, check the hose connector in the outdrive. If it is corroced, the pump will suck air and you will have cooling problems. Replace it in case of doubt, they are not expensive.

To check the accuracy of the gauges, you may want to use an infrared thermometer and check the block or the head temerature on both engines.

If you want to access the thermostat, it is located behind the heat exchanger. You will have to remove the thermostat housing (part 31 on the drawing).

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&grou p=1913&GroupList=1923,1922,1899,1901,1902,1903,1904,1900,1924,1905,1906,1907,190 8,1909,1910,1925,1926,1911,1927,1912,1913,1914,1915,1916,1917,1928,1929,1930,193 1,1932,1939,1919,1934,1935,1920,1936,1921,1937,1938,1940"

Engines temp tested at 145 deg

Engines temp tested at 145 degrees and 180 degrees - both with 140 degree thermostats(thermos tested and working @ 140). Replaced raw water pick up tubes with clear plaastic and verified good raw water flow - no bubbles. Raw water flow also verified at sea strainer.
What's next? Could this be a heat exchanger problem? any tests I can do? Other ideas?

Gary

Why are you using 140 degree t

Why are you using 140 degree thermostats? The AQ131A factory thermostat is supposed to open at 180ºF and be fully open at 197ºF. Check your engine operator's manual for details.

"Bought the boat this winter a

"Bought the boat this winter and it came with 140's installed. The starbord motor's cooling system can't keep up. Even with the 140 thermo, it runs at 180 plus. When running above 20k RPM and on plane it overheats. Tested with plastic pickup hoses and no evidence of air bubles even on plane. Any idea of what would cause this?"

"Gary, I don't know why so

"Gary, I don't know why someone would install 140º thermostats, but it seems to me that he had a problem and tried to deal with the symptoms rather than with the problem. First thing I would do is installing back the correct (180ºF) thermostats for your engine.

Now, to troubleshoot the cooling system:

1) You should verify that the hose connector in the outdrive is not corroded and it is correctly installed. Also, make sure that the o-ring at the bottom of the water tube is in good condition and that the water intake grids are clear. Then, make sure that the hose from the outdrive to the transom shield is in good condition and that the hose clamps are tight.



2) Make sure the impeller in the raw water pump is in good condition and that the cross piece 3 is in place. Also, make sure the clamp 55 is tight and that the hose 54 is in good condition. Make also sure that the seals 8, 9, 19 and 20 are in good condition.

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&group=1907&GroupList=1923,1922,1899,1901,1902,1903,1904,1900,1924,1905,1906,1907,1908,1909,1910,1925,1926,1911,1927,1912,1913,1914,1915,1916,1917,1928,1929,1930,1931,1932,1939,1919,1934,1935,1920,1936,1921,1937,1938,1940

3) Make sure the drive belt is tight; if it is loose the circulation pump may not turn fast enough.

4) Make sure the heat exchanger is not clogged or full of scale.

5) Make sure the exhaust manifold cooling passages are clear. If with scale or mud, you won't get sufficient raw water circulation through the heat exchanger (this is a common problem).

Again, make sure you get an infrared thermometer and verify that the temperatures indicated in the temperature gauges are correct."

"Thank you for helping me with

"Thank you for helping me with this issue -
Steps 1,2 & 3 are verified. Temp also verified with infa red.Can you tell me how to determine if the exhuast mainfold cooling passages are clear?

GAry"

"One way is to distonnect the

"One way is to distonnect the rubber hose between the exhaust manifold and the exhaust pipe, then look at the condition of the water passages: if blocked, that's bad news. Also, remove the raw water copper pipe under the manifold and look at the condition of the hole in the manifold: if muddy or plugged, that's no good (you can also stick a screwdriver and see how muddy it comes out). Afterwards, stick a garden hose on that hole, run water through the manifold, and see how easily (or difficult) leaves it.

On suggestion: if the exhaust manifold is plugged and you don't know its age, consider replacing it instead of "boiling" it in a radiator shop. Chances are the manifold will disintegrate during the chemical cleaning process, and even if they managage to clean it, chances are it won't last.

This is the Sierra replacement exhaust manifold, which is far cheaper than the original VP.

http://www.marineengine.com/parts/part_details.php?pnum=SIE18-1930-1&returntopag e=80240786.htm"