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AQ151A Engine Overheating

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robert_caulder

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"I have a AQ151A on a Sumerset

"I have a AQ151A on a Sumerset houseboat that is over heating. So far the things I have checked and or replaced are as follows. On the raw water system, the water intake on foot has been cleaned, strainer was clean, impeller replaced even though the impeller I removed was only one year old and in execellent condition ,oil cooler was removed and checked, no cleaning was needed. The only thing I have not checked on the raw water system is water flow through the exhaust manifold. Can I, and should I remove the hose between the exhaust manifold and the exhaust yoke to check for water flow through the exhaust manifold?

On the closed (freshwater system), I have replaced the thermostat and ran the engine with the radiator cap off, to make sure the new thermostat and water pump were functioning properly, they are.

Other information and observations: I have not noticed any water in the oil so I do not suspect a blown head gasket. I plan to run a compression test on the engine this weekend to confirm this. When starting the engine and placing my hand on various engine components, the first part of the engine that gets to hot to touch is the exhaust manifold by the number four cylinder.

My boat is on a small lake in central SC, most are powered by outboards, and no volvo penta dealers are nearby. Any advice given would be greatly appericated!

Thank's

Robert"
 
"Robert:
- What kind of te

"Robert:
- What kind of temps are you seeing?
- Under what operating conditions, idle/fast idle/cruising under load, etc are you seeing temps rise?

Jonathan"
 
"Jonathan,

I watch my gages

"Jonathan,

I watch my gages close, the engines normally run 160 to 180 from idle to 2000 rpm, if you push them to 3000 they will get up to 190 to 200, normally we cruise at 1500 rpm. The engine thats overheating now will climb to above normal after a few minutes at 1500rpm. The last two trips away from the dock I would only start it to get under a bridge and to dock the boat at the marina.

Thank's,
Robert"
 
"Check the raw water hose conn

"Check the raw water hose connector in the intermediate housing. It may be corroded and perforated, in which case the raw water pump will suck air."
 
"Robert:
I agree with El, tho

"Robert:
I agree with El, though I must point out that he is far better qualified to help than I am! I believe there are also some seals/o-rings in the intake circuit between the raw water intake and the impeller that could also be sucking air. I am not intimately familiar with your setup, but you may be able to rig a clear hose in the engine compartment before the impeller that will allow you to see air bubbles.

Jonathan"
 
"Thanks for the responses. Bas

"Thanks for the responses. Based on what I'm hearing the boat would need to be pulled to fix the problem, correct? If thats the case, I would have to hire a boat mover and I'd sure like to be on hundred percent positive thats what the problem was before going to that expense. Is there anything else I should check? By the way I'll be gong to the boat tommorrow, I'll see if it's possible to connect a hose on the inlet side of the strainer or water pump to see what happens.
Robert

Thank's Again,
Robert"
 
"Robert - Below is a link to a

"Robert - Below is a link to an exploded diagram of the cooling system including the raw water intake (I assumed you have a 151a, but I think this part is common to all). Part number 59 on the diagram/list is a small hose that I believe is the flexible connecting hose from the intake side of the impeller assembly to the pipe that runs out through the stern drive (intermediate connection?). I hope others here will help confirm or deny my thoughts here: I believe if you get a piece of clear acrylic flex tubing in that location and clamp it in place, when you run the engine through its paces you will see the air bubbles through that hose. That should give you a good idea that the problem lies in the piping or seals as El and I suggested. Try to see if you can check on the raw water hose connector visually as El suggested as well.

http://www.volvopentastore.com/Cooling-System-Induction-And-Exhaust-Manifold-Aq1 51a/dm/cart_id.302506159--session_id.528690954--store_id.366--view_id.321282

Good luck - Jonathan"
 
"A clear hose in the suction w

"A clear hose in the suction will show air bubbles if there is air ingress before the hose location. In your case, it would be easier than pulling the boat out of the water.

Another thing you may want to check is for blockage: 1) in the oil cooler tubes; 2) where the raw water enters the exhaust manifold; and 3) in the riser part of the exhaust manifold.

I assume that the impeller key is in place, as well as the cross piece between the raw water pump and the intermediate timing wheel."
 
"Thank's for the link, I w

"Thank's for the link, I will get a piece of clear hose and check to see if I can determine if the problem is before or after the impeller. The impeller was the first part I replaced. Last weekend I pulled the oil cooler and cleaned trash out of only two of the tubes, I was suprised at how clean it was. I would not have suspected a problem on the intake side because I can remove the cover from the strainer, start the engine and watch the impeller pull water into the strainer. Thank's to both of you for taking the time to respond to my problem. I will post again after I know the results of the clear hose test.
Robert"
 
"I installed the clear hose th

"I installed the clear hose this weekend, it did have air in the line. I'm now working on getting a trailer to pull the boat out for repairs. Thank's for your help.

Robert"
 
What should be the average eng

What should be the average engine temps be for Volvo 4.3 pentas? While out this weekend the port engine was around 120 and the starbord engine was 150 but went to 175 at 3000 rpm. Is the variance in engine temps normal? The starbord engine didn't exceed 175. At what temp should an engine be shut down? This was our first outing on the boat so I don't know if I've got a guage problem or something more signifcant.
 
"Sam, it would be better if yo

"Sam, it would be better if you start a new thread to post your question, as yours is a different topic.

Thank you."
 
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