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How can we prevent, diagnose, and eliminate overheating problems?

WREKS

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We will start out with Prevention. Do not assume that you can run your engine(s) in shallow water without repercussions!

So you get an overheat warning. What do you do? You may ask yourself. Where have I just been?

I started out with prevention, because I have had many overheat warnings and most of them trace back to running in the shallows and close to sandbars. The pumps swirl up the sand/sediment and push it into the cooling system. But does it all flush out? That is not to say, ingesting sand/sediment is the only cause of overheating. Anything that blocks the flow of water through the system will hopefully shut down the engine in peril. Most of the comments made in this thread regarding overheating issues focus on the cooling system.

I always flushed the engines after being on the water. The boaters that get out there and run those engines at WOT are probably going to fare much better than this old guy that that derived the most pleasure at no-wake speed constantly hearing the depth sounder alarm. One problem I find is that water often goes from deep to shallow quickly. If you spend most of the time in 5 or 6 feet, you may avoid the overheats. When you are pulling up to a sandbar, keep three feet of water under the pump.

Of course being in shallow water also means weeds and debris. Any thing blocking the flow of cooling water is the start of an overheat. If the impeller gets stuffed it loads up the engine. If the intake screen gets blocked, game over. If the flashing on an intake hose breaks off and blocks flow to the cylinder head water jackets, engine will overheat.

My unsubstantiated advice to someone that may have ingested sand/sediment from grounding out is: if the engine has cooled down and the overheat warning is gone, find some deep water and run the engine(s) at higher rpm and hopefully the higher pressure cooling water will start to dislodge some of the ingested sand/sediment. If you are still overheating, the cooling system may have to be cleaned out

I think what happened with my boat is that I thought the flushing would take care of the overheat issue. Maybe sometimes it will, but I ended up with an accumulation of sand/sediment, not salt, in the cylinder water-jackets. It became impacted It had to be scraped and chiseled out. It took hours to do this after removing the cylinder head which required removing the engine from the boat.

What I scraped and chiseled out is below the crusty buildup plainly visible in the first photo. Along with ingesting sand, anything that is smaller than the intake screen will come in. The first photo below is the cylinder block.

The second photo is the cylinder head. It too has plugged up water jackets on the exhaust side. It gets plugged with whatever made it past the intake screen. Again, this occurred on engines that were flushed after use.

Looking at the large water passages in the cylinder head and cylinder block one might ask why this buildup could accumulate although the engines were flushed?

Answer is the head gasket. It does not have the large openings that the cylinder head and the cylinder cylinder block have. I do not know why it is made that way. It blocks flow. It blocks flushing. There is a buildup of sediment/substance on both sides of the gasket. Maybe the cooling system would be even less effective if the gasket was made differently.

The conditions mentioned above are mostly about prevention. The cooling system may very well tolerate quite a bit of buildup of sand/sediment before the overheat light shut down the engines. Flushing is definitely helpful, but not the complete remedy. When the cooling system gets impacted to the extent that mine did on both engines, the only remedy became removing the cylinder head and cleaning the sand/sediment out of the water passages. That requires removing the engine(s) from the boat. That is very expensive. That can easily happen. Please respond with your experiences!

One more photo: The cooling passages of the oil cooler before cleaning.
 

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WREKS

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This part of the post is directed more to the new members and viewers.

Diagnosing an overheat can start with a short list for the cooling system: intake screen and cleanout; thermostat; hose disconnection; hose blocked or crimped. If the list was shortened even more, it would be intake screen and cleanout. The others in the list are much less likely to be a problem. There are probably other causes to be added to the list and those not related to the cooling system such as low oil or bearing problems.

It is fairly easy to process the short short list. For example: You run through a patch of lily pads; the boat bogs down a little bit but returns to normal and then all at once the rpms are cut way down and there is an overheat warning. The first thing you do is stop the engine which has, hopefully, already protected itself by going into a very low idle. Then you remove the plug below the clean out hatch and remove any plant debris. Replacing the plug and closing the hatch, you are ready to go again. Everything seems ok. Engine starts with no overheat warning and away you go. Then, before you have gone a mile, engine bogs down again and the overheat light is back on. Now what?

It starts to get more complicated. You know you have a problem and may even know what it is but it is a little more difficult to remedy.
Your guess is that something is still blocking the intake screen. Now, you may try clearing it revving the motor, but if that does not clear the blockage whatever is in there will have to be cleared by hand and maybe the boat has to be removed from the water to do it.

Adding to that, there can be debris in the water that is not as obvious as lily pads. It is possible that any debris in a certain size range floating in the water can end up blocking the cooling system. This includes plastic and cardboard trash and small pieces of wood. I was shut down on a river once because it was fall and there was an abundance of leaves floating half submerged.

Moving on, testing the thermostat can be done by removing it from the housing and observing the upper and lower setpoints as water starts to boil and cool. It may be easier observe the stream of water that appears when it opens. If the water is streaming and the engine has not registered an overheat, I think it is still good. Both of mine are thirteen years old, but I have also tested them according to the service manual specifications. Testing the heat sensors comes later.

Visual inspection for water collecting in the engine bay and beneath the cleanout tray will indicate a leak. Below the cleanout tray there is one cooling water intake hose per engine. (If this hose gets disconnected below the cleanout tray, the engine will immediately overheat and start filling that area as well as the engine bay.) I have never had that happen and do not expect it.

As far as blockage in a hose, I know of only one case where the restricted plastic t-fitting going to the bottom of the cylinder water jackets had a manufacturing defect that led to an overheat.
 
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14SX190

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Wow.
Great tutorial
 

WREKS

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@14SX190 Thanks Hope you're making progress with the milky oil issue.
 

tdonoughue

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Nice write-up and photos (yuck)! So, how did you come to disassemble your engine to find all of that? Just continued cooling issues having eliminated the other causes?
 

WREKS

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@tdonoughue Thanks for the commendation!
To answer your question: My wife and I were discouraged. Our boat was just taking up space. We could not afford to have it repaired. But I had been thinking for a long time about how I could remove the engine(s). And, over time, I was able to build a rather light weight aluminum gantry crane and I removed the engines. Port had milky oil. Starboard had an overheat. Both were chock full of sand/sediment. Milky oil is documented on this site. Both issues have been resolved. I only have 17 miles on the milky oil fix, but I think it will hold. To many of us the expense of these repairs may be insurmountable. And that is why I am so concerned about overheat prevention.
 

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WREKS

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@tdonoughue I would definitely like to try it.

I think it would be easy enough to determine its effectiveness, at least on the MR-1s.

The back oil cooler cover can be removed with a little effort. After coming off the water, remove the back oil cooler cover and observe any buildup of scale on the cover.

Reinstall the cover and try the product. After completing the instructions, remove the cover and observe the results.

It looks like you might be able to do such a test on your 1.8s.
 

WREKS

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Diagnosing overheating that happens almost immediately:

So far, everything mentioned is external to the engine. When the externals have been ruled out, then Diagnosing requires various experts from JBN and various tools including an infra red thermometer.

One way an overheat occurs is very quickly. For instance, you just left the dock, hardly got on plane and the rpms drastically reduce. What happened!

If you have an infrared thermometer, you can start taking readings at various places on the engine. Best place to start is the exhaust manifold, because that is closest to the heat of combustion. The rest of the engine hardly got a chance to heat up before it was getting shutdown. If you know where the engine thermoswitch is located, then you can point the thermometer in that area. The engine cools relatively quickly, so once you find a hot spot, if you do, scan along the exhaust manifold at the same level to see how the temperature varies. Is it just one place or does it extend along the manifold? The indication here is that a water jacket, passage or both are blocked.

This diagnosis could probably be determined before the boat is even in the water, by running it on the hose. If you store your boat near a water connection, that may be the best thing to do before launching it; let the engine(s) run a bit-at least long enough for the thermostat(s) to open. You know they are open when the pilot starts dribbling water.

I do not assume that the boat will be as I left it. What was a soft, loose clog in the cooling system, even after flushing, may harden into something quite immovable over time.
 
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WREKS

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Diagnosing overheating that happens after an engine has been running for a while.

For example: The engine has been running above no-wake speed for a sustained period of time. If an overheat occurs after running a while and no other cause is evident such as cooling water leaking in or into the engine bay, then it is very possible that engine heat is building up caused by an internal blockage in the cooling system including the exhaust manifolds.

The cooling water flow cannot carry off enough heat and finally surpasses the sensor threshold. The normally open engine or exhaust thermo-switch closes and limits the rpm to a rough idle. If you have two engines, their temperatures should be roughly the same. If by comparing their temperatures one is running significantly hotter than the other, that temperature difference may indicate an internal blockage that is causing the overheat. That could be determined by taking temperature readings at the same location on each engine and comparing them.

Here is a likely scenario that leads to a slow overheat. You cruise through some shallow water and the pump pushes a little sand/silt into the cooling water jackets surrounding the cylinders. You do not know this because you do not get an overheat warning. Furthermore, according to what you have been told, your boat will float in 18" of water. You go home, flush the motor, and store the boat for a few weeks before using it again. Maybe you do this a few times. Then one day you go out and for whatever reason, you do not know, the engine overheats. You immediately take the boat out of the water, flush it, and start to wonder why it overheated. You flushed it every time you used it. Why did it start overheating?

Your cooling system is not built to pass sand and silt. If it was it would have polished and smooth surfaces not rough cast aluminum with sharp corners, dead ends, and gaskets with small openings blocking the flow. Your cooling system is made for water flow, even salt water flow, nothing else. If suspended particles make it through, do not think that it will work that way indefinitely.

Now, I think, it is very possible to flush out most newly ingested sand/silt. But this should be done immediately on the water by running at high speed, not waiting until you get home and block off the intake in order to increase the cooling system pressure. If salt/silt gets into the system and can accumulate little by little, the engine heat, especially overheat, will bake it in. Then removing it requires, removing the engine from the boat and removing the cylinder head.
 
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WREKS

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Eliminating Overheating due to ingestion of sand/silt by running on plane.

The best time to eliminate an overheating problem in the cooling system is as soon as it occurs. Do not get an overheat warning, shut down and immediately remove the boat from the water. Try to diagnose the problem. If you determine it is cooling system related, such as ingesting sand/silt in shallow water, allow the motor to cool down and clear the alarm. Then, as long as you do not go into alarm again, run in some deeper water for thirty or more minutes on plane. Hopefully it will expel whatever caused the overheat.

Not taking care of the overheat problem, immediately, allows the sand/silt to settle in, dry out from residual engine heat, and become hard. Flushing on the hose, later will probably be 'too little too late.' Then every time thereafter an overheat occurs, the engine heat will further bake it in, cooking instead of cooling. With an engine overheat, 'NOW' is always the time to try to eliminate it.
 

demeaux

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Thanks for all the great information! ***LOCATION OF SENSORS??*** I have a 2012 SX210 with the 1052cc engines. Boat will run flawlessly all day long between 6k-6500k RPM. If I run 7k+ the starboard engine goes into limp mode usually within 2-5 minutes. After a quick shut down, and restart everything is fine as long as I stay under 7k RPM. Also I have good and constant water flow from pee holes.

I've completed the following trying to correct the problem...Engines have around 120 hours on them

1. Cleaned the screen located at the pump nozzle (no obstructions)
2. Clean out hoses connected to pee holes (no obstructions)
3. Changed thermostats
4. Changed oil and filters (did not overfill)
5. Changed spark plugs
6. Checked air filters (still look brand new, no oil present or obstructions)

After reading countless threads I'm wondering if I there's an obstruction in the cooling system or bad sensors. I would like to start with he easiest possible fix first. lol. Can someone post the locations of the Thermo Sensors and Air temp sensors? My plan is too switch with them with the port engine and see if the alarm will trip. If it does then I assume it has to be the cooling system. From there I will start pulling hoses checking for obstructions. Any tips or information would be appreciated.
 

WREKS

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It is not easy to get to the engine thermoswitch without removing the engine. It is tucked up behind the exhaust manifold by cylinder no. 1. If you have an infrared heat gun (Harbor Freight), try to compare the cylinder block and exhaust pipe temperatures of both engines at the 6k+ rpm threshold.
 

WREKS

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Eliminating Overheating due to white algae buildup.
Recently, I had a problem with my home air conditioning. The condensate line got clogged, started to back up, and was leaking in the garage.
The service company told me that the condensate line can get clogged from algae growth and has to be vacuumed out if the algae builds up. The algae has a white slimy appearance. When I talked with the AC tech about preventing the algae build up, he suggested pouring a half cup of vinegar a couple times a month into the line where it starts at the air handler.

There are several photos at the beginning of this thread in post #1, they show a substance on the gaskets and the oil cooler cover. It does not appear to be sand, salt, or sediment. It is soft and white or clear like silicone. What happens with my AC condensate line leads me to believe that the same thing is happening when the engine is cold. After the engine stops running, the warm wet environment of an open loop cooling system provides the perfect environment for internal algae build up. Even if the cooling system drains down, there is still an abundance of moisture left inside the cooling water passages. Here is a photo of the portside oil cooler cover. Conditions: The boat sits covered along side my house; The engine bay is always dry; May 1, 2020 was the last time it was on the water; The oil cover was clean when I launched the boat to test run it after fixing a milky-oil problem; After that, the engines were run on the hose for 5-10 minutes apiece semimonthly during the lay up. This is what the oil cooler cover looks like now after running for 10 minutes on a salt removal solution.

1604349746766.png

I do not know what happens to the algae after it dries out, but I think it turns brown and scales, leading to constrictions in the water jackets. I have observed algae in a soft form throughout the oil cooler, exhaust cooling ports, both sides of the head gasket, and thermostat. It does not appear to present in the cylinder water jackets in the soft form. Along with sand, salt, and sediment, algae build up can contribute to engine overheating.

Now I am pursuing ways to prevent or eliminate internal algae build up. I am sure that flushing with dish soap, vinegar, and various products are beneficial. Recently, the portside thermostat plugged twice, when I began running the engine on the hose. The first time, I stopped the engine, removed the thermostat, and cleared the plug. The second time, while it was running. I used an air bulb to backflush the thermostat through the water pilot opening. That worked. I think compressed air could do the same. I have removed the intake screen, plugged the cooling water supply hole in the impeller housing, and filled the cooling system with white vinegar through the flush port. A week from now, I will drain the cooling system at the impeller housing, flush the engines with dish soap, and remove the oil cooler cover to see if any of the buildup pictured above gets removed.

Looking for ideas and suggestions.
 
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Cambo

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@WREKS are you the original owner of that 2007sx ? that build up looks like it was caused due to not flushing the motors . The different salinity levels of the salt water, sand mud and silt types will most likely impact build up as well . You mentioned milky oil did you check your exhaust manifold for breaches see below the yellow arrow points to a hole in the exhaust manifold this allows some water into the cylinder to pass by the rings and get into the oil ,


exh.jpg
 

WREKS

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@Cambo Thanks for response. Before the boat went in the water, I removed port side engine to repair the milky-oil problem. That is documented here: Milky oil repair. While the engine was out of the boat, I removed and thoroughly cleaned the oil cooler. At the very end of April, I took the boat out for a water test. It passed and no milky oil since then. I was only out for a few hours and flushed each engine for ten minutes afterward. Since then, I regularly flush the engines on the hose every other week. This internal buildup has occurred while the boat is out of the water. And Yes. I am the original owner.
 

14SX190

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That oil cooler needs a culture. Could it be hard water building up scale from hose water?
That would not be new if source to flush is the same.

That is one odd issue.
 

WREKS

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@14SX190 I am on city water. When we are done flushing theses engines, they just sit until we go back out. When we flush them, we may use a salt remover, but they still probably end up with fresh water in them, slowly draining out, but never really drying out. That is the perfect environment for algae buildup, cool, dark passageways with plenty of surface area.
 

14SX190

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Are you boating in brackish water or areas known about growth. I don't know what is called but FWC is all about how and where to flush.

I'm sure your area and years boating this is isolated to unknown cause if symptoms started on same boat.

It definitely warrants investigation and worries
 

WREKS

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Boat was in the water for 3 hours in Stuart, Fl area, then sat for 5 months after that. I believe it is similar to the algae that has to be vacuumed out of pluged AC condensate lines. That is much easier than trying to flush it out of a Yamaha jetboat engine.
 
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