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1981 AQ145 Heat Exchanger Addition

E

ericfragola

New member
Hi all,

I am having heat issues with my 81 Volvo Penta. It's a 4 cylinder AQ145. If I go above 1800 RPM's, the heat starts to rise greatly. It stays around 180 degrees. Once I go over 1800 RPM's, it starts to heat up way and will even go to 220.

I would like to add an extra heat exchanger in series to add additional cooling to the motor to prevent from overheating. Has anyone done this and/or have any recommendations/suggestions on what I should do? I have attached two photos to help picture my theory on what I plan to do
Here is my current understanding in a simplified drawing of how the raw water cooling system works. current path.jpg
Here is my intended plan for adding an additional exchanger in series to the current onewith new exchanger.jpg

Any input is greatly appreciated. Thanks!

Eric
 
If everything is working as it should you don't need extra cooling components.

When you say the heat rises with the RPMs, are you talking while the boat is being used? Or in a barrel? If the temps rise when the boat is on the water and stepping up on plane, check the water intake goose neck on the drive. Chances are the insides have corroded to a point where the pump is sucking air instead of water. No extra cooling components will help this condition. The part is cheap and easily replaced.

If the heat is rising with the motor running while the drive is in a barrel you need to check other components, ie, raw water pump impellor, exhaust manifold for blockage, heat exchanger for blockage, etc.

My little AQ120 pushes 5500 lbs and never gets above 195 degrees even at WOT. I have replaced the gooseneck. I have rebuilt the water pump and replaced the ex. manifold when they needed it. Everything works as it should.
 
I'm thinking plugged exhaust manifold. As Sounder said, this engine should run at normal temps with no added cooling at all. Somethings not right.
 
What Volvo Penta designed as OEM works perfectly on this engine.
You'll need to find out what's wrong and/or what is not working, and then correct it!


Just to name several areas/items:

**Water neck fitting and special beaded gasket (this is a "wear item".... have either been replaced?)
Exhaust manifold (seawater ports and mixing chamber clear?)
Seawater pump (impeller and cam OK?)
Heat Exchanger passages (are these clean and clear?)
Oil Cooler (are the seawater passages clear?)

** The water neck fitting raises up out of the water once up on plane.
If corrosion has caused the slightest suction breach here, the seawater pump will not function.


If you have issues at any of these areas, a second heat exchanger will be futile.




.
 
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My link to the water neck fitting is not working.
Here's an AQ series drive water neck fitting.

images


The fitting and beaded gasket need to be replaced routinely.

If there is excessive play/slop at the upper pivot tube bushing, the beaded gasket may fail shortly, and will breach suction.


.
 
pugetsounder said:
If everything is working as it should you don't need extra cooling components.

When you say the heat rises with the RPMs, are you talking while the boat is being used? Or in a barrel? If the temps rise when the boat is on the water and stepping up on plane, check the water intake goose neck on the drive. Chances are the insides have corroded to a point where the pump is sucking air instead of water. No extra cooling components will help this condition. The part is cheap and easily replaced.

If the heat is rising with the motor running while the drive is in a barrel you need to check other components, ie, raw water pump impellor, exhaust manifold for blockage, heat exchanger for blockage, etc.

My little AQ120 pushes 5500 lbs and never gets above 195 degrees even at WOT. I have replaced the gooseneck. I have rebuilt the water pump and replaced the ex. manifold when they needed it. Everything works as it should.
Click to expand...


See that's what i figured. I should be able to go way above 1800 rpms and not have a heat issue. The previous owner did MINIMAL maintenance to the boat. Engine and interior wise. Also this is at 1800 rpms when driving. Have not checked it in neutral to see if the same thing happens at 1800 rpms.

What I have done so far -
1. Replaced the raw water impeller (which was torn up when bought), and flushed the system of all the old rubber impeller pieces that clogged the metal line from the raw water pump to heat exchanger.
2. Pulled the coolant pump and inspected it - everything looks good.
3. Pulled the heat exchanger and replaces all gaskets and inspected the core. From what I can tell its fine.
4. Replaced thermostat.

What it sounds like I need to do
1. Check the raw water intake goose neck.
2. Check the exhaust manifold for any plugging.
 
RicardoMarine said:
What Volvo Penta designed as OEM works perfectly on this engine.
You'll need to find out what's wrong and/or what is not working, and then correct it!


Just to name several areas/items:

**Water neck fitting and special beaded gasket (this is a "wear item".... have either been replaced?)
Exhaust manifold (seawater ports and mixing chamber clear?)
Seawater pump (impeller and cam OK?)
Heat Exchanger passages (are these clean and clear?)
Oil Cooler (are the seawater passages clear?)

** The water neck fitting raises up out of the water once up on plane.
If corrosion has caused the slightest suction breach here, the seawater pump will not function.


If you have issues at any of these areas, a second heat exchanger will be futile.




.
Click to expand...


I will go up the boat and check these out today. These are things that have not been looked at yet. Thanks for the input, thisis exactly why I posted this topic in here. Now that I have a list of things to check out I'll go do so and reply with my findings. Thanks everyone. Very valuable information put in here.

Will update later today with my findings.
 
The 4cyl OHV manifolds are hard to determine if clogged or not but that's where I'd put my money. I've seen way to many that look good but wouldn't flow.
 
From what he's describing I would say it's the gooseneck fitting. If it runs cool while idling around in the water then only heats up when on plane that's the classic symptom. That's also a lot cheaper fix, I would start there. I bought one for $30 delivered. Part number VP 854031 or Sierra 18-2777

I aslo believe the AQ145 is an OHC motor, pull the drain plug on the bottom of the manifold and stick a coat hanger up the hole, you will always be surprised how much scale accumulates.
 
....................
pugetsounder said:
From what he's describing I would say it's the gooseneck fitting.
Water neck fitting. :D

If it runs cool while idling around in the water then only heats up when on plane that's the classic symptom.
Yes... as I said earlier, the water neck fitting raises up and out of the water once the boat is on plane.
If it has breached suction, the seawater pump will stop pulling water in while up and out while on plane.
However, it will pull water in as long as the entire area is submerged.


I aslo believe the AQ145 is an OHC motor,
Yes.

pull the drain plug on the bottom of the manifold and stick a coat hanger up the hole, you will always be surprised how much scale accumulates.
Agree. However, even with a clear drain port, if the mixing chamber at the rear of the manifold is fouled up, it will restrict seawater flow.


My money is on the water neck fitting.... aka goose neck! :D
Click to expand...
 
IF by chance you do need a new ex. manifold here is a good price:

http://www.marineparts.com/c-458-os...40-b20-23-and-25-liter-855387-7-834438-4.aspx

As Rick said the rear end of them can corrode especially in saltwater use. Or even worse they don't get properly drained for the winter and can crack inside. This can possibly cause hydrolock when your motor is running by allowing water to flow back into the cylinders. The manifold is designed to keep water out of the engine until it corrodes to the point of not being able to.
 
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boatdoc55 said:
The 4cyl OHV manifolds are hard to determine if clogged or not but that's where I'd put my money. I've seen way to many that look good but wouldn't flow.
Click to expand...

Ok, so I pulled the exhaust manifold. The drain plug was clogged, but that was it. I took a water bottle and squeezed water into the port where the raw water normally goes into. It came out of all 4 ports in the back just fine. I did not see anything of too much concern there. Although thank you pugetsounder for the link to a new exhaust manifold. If all else fails I may be looking into getting a new one just to eliminate the factor. As of right now, i've checked it and it appears to be working good. But from the looks of it, it could use a replacement within the next couple of year. Just from the rusting and wearing of it.


"From what he's describing I would say it's the gooseneck fitting. If it runs cool while idling around in the water then only heats up when on plane that's the classic symptom. That's also a lot cheaper fix, I would start there. I bought one for $30 delivered. Part number VP 854031 or Sierra 18-2777" I did not get a chance to check the gooseneck/water neck fitting. I spent my day taking off the exhaust manifold and cleaning the oil cooler. Although that will be my next inspection.

Oil Cooler - was very restrictive. It was clogged pretty well with tiny little rocks/seashell pieces. Only 5 of the tubes I could actually see through and were completely clear. I took a piece of wire and rodded out each and every tube and flushed out the oil cooler. After putting the exhaust manifold back on and the oil cooler back together, I took her for a spin. Brought it up to 2400 rpms now and it stayed around 195. But anything above that the temps started to creep over 200 and I got a bit of smoke coming from the exhaust.

So far, Everything from the raw water pump and out, appears good. I did find that plugging in the oil cooler which has helped some. I have yet to check to water intake side, although it sounds very promising that the inlet is bad. Where exactly does it go into the boat from the water? Also, this boat is only being driven in fresh lake water.

Here are some photos of my findings -

1. The bottom of the oil cooler with a bunch of small pieces that clogged the tubes -Bottom of Oil Cooler.jpg

2. Here is a view of the bottom of the oil cooler. pretty well clogged.20140910_150100.jpg

3. Also, found this. What is this nipple for? Nothing was hooked up to it. What is this.jpg Here's a close up Nipple.jpg
 
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3 Hoses on the outside. Top is driveline bellows, middle is water intake, bottom is exhaust. The nipple we all talk about is right under the top bellows. It has the middle intake hose on it and the other end is clamped to the water tube coming out of the transom shield on the Starboard side. This nipple is a constant problem. The hose seldom go's bad.
The nipple on the block is a block drain, no worries here.
 
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