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Aq131 No Oil Cooler and overheating

J

jpbarrett_ct

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"I have a 1985/86 Aq131 I'

"I have a 1985/86 Aq131 I'm trying to rehab that has overheating problem, of course. In diagnosing problem a few questions have arisen:
1. is it possible I have no oil cooler on this engine? I have manual that says it does but when I look around starboard side of engine near oil filter I don't see anything resembling pictures. Should one be there? Could it have been removed?
2. Oil pressure rises quickly on gauge as RPM's rise even in neutral. I would expect that oil pressure should stay steady like a car's regardless of RPM's, no? Any ideas of what this could this indicate?
3. Manual says that overheating could be caused by excessive oil in crankcase. How can I see if this is cause and how to alleviate?

Any help is greatly appreciated!

Jim"
 
"1) There is no oil cooler

"1) There is no oil cooler on the AQ131. Your manual probably refers to the AQ151.

2) It is normal for the oil pressure to increase with the RPM, and the increase in pressure is even more significant when the engine has been run hard.

3) Like in cars, the oil disptick tells you what the adequate oil level is.

Now back to basics: why do you say that your engine is overheating? If you had high coolant temperature, check the hose connector in the outdrive and the raw water pump impeller. The hose connector tends to corrode and if it gets perforated you will get air into the raw water cooling system; and if the raw water pump impeller is no good, then there will not be enough raw water circulating through the heat exchanger."
 
"Thanks for quick response.

"Thanks for quick response.

Classic overheating - only when at WOT (4k RPM) and on plane.

Having read your helpful past responses on overheating I did recently replace the hose connector. Haven't put it back in water since then so not sure if that was it - though old connector looked in fine shape. Heat exchanger was boiled last year. Impeller new at same time.

Running in driveway in bucket of water to see if I can see leaks or if it is sucking in air at other points of sterndrive. But appears that water is circulating well though hard to gauge - didn't overheat at 3,500 RPM. Though coolant expanded such that it overflowed when I removed cap. Coolant reservoir/heat exchanger jury-rigged by previous owner - face plate was welded shut for some odd reason. Still wonder if I should replace that whole unit (there's no overflow reservoir - is that typical?)

Coolant gets hot - so its circulating. Raw water is warm out of sterndrive exhaust - so its capturing heat. Worst case, could engine itself be simply producing excessive heat due to age/wear/tear/fricition?

Thoughts?"
 
"Your arrangement seems the st

"Your arrangement seems the standard AQ131.

If you have read my previous posts, typical causes for overheating are 1) a bad o-ring around the water tube between the lower and intermediate units in the outdrive; 2) a corroded hose connector; 3) a defective hose between the outdrive and the transom shield; 4) loose hose clamps or flanges in the suction line between the transom shield and the raw water pump; 5) defective raw water pump (usually a bad impeller); 6) clogged strainer before heat exchanger; 7) choked heat exchanger; 8) plugged-up exhaust manifold due to internal corrosion; 9) defective fresh water pump; 10) loose alternator belt; and 11) a bad thermostat.

Now you have some home work to do and find out which of the above is causing the overheating."
 
"You ran your engine at 3500 R

"You ran your engine at 3500 RPM on a hose or on a bucket,wow, brave person. That's a no load situation and not good for your engine.
Heat in the high RPM range in most cases I 've been involved with points right at the exhaust manifold/manifolds. Do you know how old this manifold is?"
 
"Not brave - ignorant. Thanks

"Not brave - ignorant. Thanks for warning.

Exhaust manifold is brand new - replaced last year.

Running in driveway today I noticed funny thing - coolant overflowing at only 160 degrees - barely hot/warm.

Coolant reservoir/heat exchanger, as mentioned, was jury-rigged and welded together. Neck on reservoir was corroded and re-built. Is it just a bad seal allowing coolant to escape at lower temps or is it pointing to part of problem?

Also have small leak at raw water impeller gasket throwing drops of water around, which increases with higher RPM's. I'm going to take that apart to make sure there is better seal - could be point of ingress of air?"
 
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