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20degree F while idling back down when running

R

Rick Davis

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"Older 4 cylinder Volvo with t

"Older 4 cylinder Volvo with twin carbs, AQ151 according to engine records from previous owner. 1200 rpm and above temperature 180degree F and stable . 1200 rpm and down through idle 950 rpm temperature rises to 200 to 205 degree F. up and down in temp is rapid , 90 seconds or so. Run in back yard with garden hose and ears on out drive. Bottom hole plugged.

You guys helped last summer with good advice. Over heated up to 235 degree F at idle , ok 180 F when running . Motor hydrolocked at dock and sheared pin in camshaft pully. Replaced , timed and running good and strong now.

Exhaust Manifold replaced, raw water pump replaced. Coolant level fine and 50 50 mix.
Any ideas? I would feel more comfortable with temp steady but is this +20 temp rise a problem to be worried about?

Rick"
 
"Thanks,

Appears clean and

"Thanks,

Appears clean and not sure how old stat is but the guy I bought it from seemed to have changed it recently based on receipts.

Rick"
 
also forgot to mention that th

also forgot to mention that the water exiting the exhaust is minimal at idle and increases quite a bit at higher rpms. Perhaps it has blockage somewhere?
 
"I doubt a blockage as You men

"I doubt a blockage as You mention new manifold. If the water out encreases almost with the rpm, that is not likely the case. But it might be the capacity of the circulation pump. I would have changed that one. Furthermore have a look at the raw water pump. There are different cams, and some kits include both types. The thin ones behaves like You describe, the thicker ones gives more at idle, but may loose a bit at higher rpms."
 
"I am wondering if the raw wat

"I am wondering if the raw water pump could be sucking air somehow. You may want to verify that the hose 88 connecting the copper pipe to the tube 41 is in good condition (no cracks or holes) and that the hose clamps are tight. I don't think that the problem is in the hose 40 or the hose connector 99, as they should be under water when the boat is not planing, but you may want to check them as well.

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&grou p=1924&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

In the next link, make sure that the hose clamp 55 is tight, and that the gaskets # 9 are in good condition, especially on the suction side of the pump. Also, you may want to verify that the cross piece # 3 is in good condition, although I do not expect it to be the cause of the problem you are experiencing.

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&grou p=1907&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"
 
"Thank you gentlemen I appreci

"Thank you gentlemen I appreciate all the input. I will check these items. If it was not for the limited raw water flow at idle I would jump in and change the fresh water pump. I was leaning towards restriction on the input side somewhere in the outdrive. If so what would the liability be using a thru hull water
supply , clam shell and strainer? Does the incoming raw water cool the oil in the outdrive at all?
Over all is the 20 degree up to 200 F a serious concern? The Oil is 10W 40W and reading your viscosity discussions this would be less resitance while trolling , which is hour after hour. Thanks again."
 
"I would not use a through-hul

"I would not use a through-hull water intake. With the VP arrangement, your boat won't sink if something ruptures in the raw water suction side and the boat stops, as the tube coming inboard from the transom shield is above or nearly above water.

The 20 degree temporary increse in water temperature is not necessarily a concern, but it could be an indication of something not being right in the cooling system; and that "something" could turn into a concern if not dealt with on time."
 
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