Over Heat Alarm ! What To Try Next

[Steveditt]

1998 s 175 TXRW which I have owned for five years has been great today I was towed in by Boat /Us because of an overheat alarm.
1, 2017 new thermostats ,complete water pump used the boat all May no issues today after running 15 minutes over heat alarm ,cooled restarted few minutes alarm.
2,removed thermostats no change few minutes alarm ,called for tow.
3,at the dock ,opened both thermostat housings strong flow of water from hose water to one thermostat housing came out lower unit ,tell tail ,filled other thermostat housing and water came out .
4, Connected hose to flush out connection ,water flowed tail tell ,low unit and out both thermostat housings
5, Started engine tail tell ,low unit and both thermostat housing had water coming out .So what's next.
6, should I use a external thermal reader ? Does the thermo sensor activate alarm or either of the two thermo switches ?
I know what it can be salt in the water passages hoping not . Thanks for any help .

[Jason2tpa]

Sounds like you've confirmed water pump is doing its job, however, this does not imply water is completely circulating either or both banks. The thermoswitch grounding in either bank will cause the alarm to activate. To determine which bank is overheating you could use an external thermal gun. If you don't have one, try disconnecting one sensor at a time while running engine on flush. See which banks sensor is activating alarm.

Your engine is near 20 years old, and you've had it for the past 5 years. If you haven't pulled the head covers while owning the engine do you know if the previous owner did? It's not a preventative maintenance procedure, therefore it's usually only done when overheating or a gasket leak has occurred.

You could run a product like Salt-X or likewise through the flush, see if this helps any. But if you haven't pulled the head covers to inspect the cooling system since owning the engine it's no big job to do. Just be careful when unlocking each head bolt. Depending on the condition of the gaskets, probably a good idea to replace while the covers are off. They are fairly inexpensive.

[FabricGATOR]

The thermo sensor send information to the ECU and the thermo switches are what triggers the alarm.

The switches are pushed into a hole embossed in the head and sealed with a rubber plug. You will see two wires coming out of the black rubber plug at the top of each cylinder head.

When you overheat, the temperature rises to a point where the thermo switch closes and allows continuity to flow to the alarm. You can test this by disconnecting the (two each side) bullet connectors from the switch and jumpering the connectors on the engine side of wire harness to simulate the overheat condition and sound the alarm.
You can test the thermo switches by removing them and with a continuity meter and thermometer, heat them in water observing when they close the contact.

Most likely you are fouled with salt and minerals. This may be treated with a chemical solution such as citric acid, RidLyme or salt away.

I have used RidLyme successfully in the past by removing the lowerunit, removing the thermostats, and attaching a hose to the cooling water pipe from where the water pump attaches to the upper casing /engine. I then used a spare bilge pump to circulate the solution from a bucket up and through the engine water passages. Use plastic film or a cut garbage bag to contain and redirect all the solution back into the bucket. Circulate for hours. In the beginning you may get foam, this is indication that it is working and it should calm down in a while. Think like dissolving a cough drop in your mouth, over time it slowly dissolves away until there is nothing.

To test your solution to see if it is still working, try an oyster shell or even a tums antacid tablet to see if it makes a sample bubble. No bubbles and your solution has become neutral. Prepare a fresh batch and continue. You should be able to see the progress through the thermostat hole. Remember, the thermostat is where the majority of the water flows, so after it is clean, you probably need to continue because the area of less circulation are probably still fouled.

Now, when I return and back the boat into the driveway, I always connect a hose to the flush port ASAP and then continue to disconnect the truck from the trailer. If I am in a hurry and wash nothing else, I always try to get the fresh water flush started as soon as possible.

Bon Chance!

[Steveditt]

Sounds like you've confirmed water pump is doing its job, however, this does not imply water is completely circulating either or both banks. The thermoswitch grounding in either bank will cause the alarm to activate. To determine which bank is overheating you could use an external thermal gun. If you don't have one, try disconnecting one sensor at a time while running engine on flush. See which banks sensor is activating alarm.

Your engine is near 20 years old, and you've had it for the past 5 years. If you haven't pulled the head covers while owning the engine do you know if the previous owner did? It's not a preventative maintenance procedure, therefore it's usually only done when overheating or a gasket leak has occurred.

You could run a product like Salt-X or likewise through the flush, see if this helps any. But if you haven't pulled the head covers to inspect the cooling system since owning the engine it's no big job to do. Just be careful when unlocking each head bolt. Depending on the condition of the gaskets, probably a good idea to replace while the covers are off. They are fairly inexpensive.

Thanks I really appreciate your response , I expect the worse as I don't think the previous owner did much ,spoke to two local Yamaha dealers prior to the problem about removing the head both said it might cause expensive damage if you have to deal with the problem when it happens . Located a thermal tester .Thanks again

[TownsendsFJR1300]

Agreed, the heads and mostly lower cylinder passages are salt clogged.

Once they get completely clogged, getting a salt dissolving liquid is about impossible.

Generally (IME), you usually get a higher RPM over heat first, (plus 4,200), you shut down -re-start and you good again till the higher RPMs.

The actual fix is not hard, (yanking the heads), but being VERY CAREFUL, (using heat, etc) when removing the bolts will be your biggest challenge (not breaking them)

A lazer temp gun aimed at different area's of the cylinders (while running) will likely show much higher temps where the cylinder meets the head (point at cylinder).

[Steveditt]

The thermo sensor send information to the ECU and the thermo switches are what triggers the alarm.

The switches are pushed into a hole embossed in the head and sealed with a rubber plug. You will see two wires coming out of the black rubber plug at the top of each cylinder head.

When you overheat, the temperature rises to a point where the thermo switch closes and allows continuity to flow to the alarm. You can test this by disconnecting the (two each side) bullet connectors from the switch and jumpering the connectors on the engine side of wire harness to simulate the overheat condition and sound the alarm.
You can test the thermo switches by removing them and with a continuity meter and thermometer, heat them in water observing when they close the contact.

Most likely you are fouled with salt and minerals. This may be treated with a chemical solution such as citric acid, RidLyme or salt away.

I have used RidLyme successfully in the past by removing the lowerunit, removing the thermostats, and attaching a hose to the cooling water pipe from where the water pump attaches to the upper casing /engine. I then used a spare bilge pump to circulate the solution from a bucket up and through the engine water passages. Use plastic film or a cut garbage bag to contain and redirect all the solution back into the bucket. Circulate for hours. In the beginning you may get foam, this is indication that it is working and it should calm down in a while. Think like dissolving a cough drop in your mouth, over time it slowly dissolves away until there is nothing.

To test your solution to see if it is still working, try an oyster shell or even a tums antacid tablet to see if it makes a sample bubble. No bubbles and your solution has become neutral. Prepare a fresh batch and continue. You should be able to see the progress through the thermostat hole. Remember, the thermostat is where the majority of the water flows, so after it is clean, you probably need to continue because the area of less circulation are probably still fouled.

Now, when I return and back the boat into the driveway, I always connect a hose to the flush port ASAP and then continue to disconnect the truck from the trailer. If I am in a hurry and wash nothing else, I always try to get the fresh water flush started as soon as possible.

Bon Chance!

Certainly some great information ,when you using the solution pumping up through the engine should I remove both thermostat housing ?I have located a thermal heat gun so Ill check that first . My boat in a slip about a hour away . Does the flush attachment side of the engine provide enough water to the head for cooling while running ,this would eliminate the water pump which is new ? Thanks again for your help !

[TownsendsFJR1300]

Citric acid:

http://www.yamahaoutboardparts.com/f...h27868-p2.html


http://www.yamahaoutboardparts.com/f...g-th19434.html


http://www.yamahaoutboardparts.com/f...m-th23666.html



.

[99yam40]

Certainly some great information ,when you using the solution pumping up through the engine should I remove both thermostat housing ?I have located a thermal heat gun so Ill check that first . My boat in a slip about a hour away . Does the flush attachment side of the engine provide enough water to the head for cooling while running ,this would eliminate the water pump which is new ? Thanks again for your help !

You remove the stats and put the housings back on.
if left off the solution would run out all over the motor

owners manual warns against running motor without water to the pump ,as it could damage it

[Jason2tpa]

Thanks I really appreciate your response , I expect the worse as I don't think the previous owner did much ,spoke to two local Yamaha dealers prior to the problem about removing the head both said it might cause expensive damage if you have to deal with the problem when it happens . Located a thermal tester .Thanks again

If the dealers are implying that removing the head covers to clean the cooling passages is expensive, then I recon the expense would be the labor charge. But if you're comfortable doing this yourself it costs you nothing. Fairly simple task too.

[TownsendsFJR1300]

Several years ago, my neighbors 200 Yammy needed the salt cleaned out. The shop wanted $800.00

We yanked both heads, no broken bolts, maybe $100 in all gaskets, bunch of time scraping salt (monotonous) but really, as noted above simple.

The lower end of the block (water jackets) were completely clogged. Amazing it ran as good as it did...

[FabricGATOR]

Certainly some great information ,when....

....Does the flush attachment side of the engine provide enough water to the head for cooling while running ,this would eliminate the water pump which is new ? Thanks again for your help !

I do not recommend running the engine without either the lower unit in the water or with the ear muffs attached to a garden hose... ever, not even for a scant second.

The rubber impeller is in a stainless steel housing attached to the lower unit. This basically, is your new water pump. The lower unit drive shaft is always turning when the engine is running and thus the water pump is always turning. When you run the engine, even for a short few seconds without that water pump wet, the friction creates heat very fast and destroys/cooks/eats/melts you impeller and transfers melted rubber to the waterpump stainless steel cup and plate.

Now if you want to remove the lower unit and then try to run the engine on the flush hose... I might try that, but I would monitor it closely and be ready to shut it down.. I take that back, I think the cooling water will fall out of the engine through the cooling water pipe that the lower unit (water pump) attaches to.

[Steveditt]

I'm kind of in the middle ,I'm fine doing the work until things go wrong and which is a good possibility {snapping bolts } ,I have service manual and usually try to do most repairs but this makes me nervous . First I'll check the head temps with the thermal gun and then decide if there is a reason to test the two thermal switches ,just to add to the problem ,I had completely new brake system installed in my trailer and tires got it home and said I'm replacing all the rollers removed them and the next day the over heat . Monday ordering 28 rollers ,if the tests indicate a clogged head then I'll bring it home and try the hail Mary Rydlyme flush removing the lower unit . If that doesn't work I think I will give in to the professional .I certainly appreciate the help !

[HarriesDGH]

If the dealers are implying that removing the head covers to clean the cooling passages is expensive, then I recon the expense would be the labor charge. But if you're comfortable doing this yourself it costs you nothing. Fairly simple task too.

I agree. I have just taken the head covers and cylinder heads off my twin 115hp V4s, and it was very straightforward. I'm not an engineer, but this was well within my competence range. All the bolts were well greased so they came off easily. Both engines had a lot of salt & debris around the cooling channels. Spent a couple of hours scraping and cleaning and they're looking good. All gaskets will need replacing.

A question. One engine had two gaskets on each side. I will replace with two, but I would be interested to know why this is the case. Finally, will I need to use any adhesive when I replace the gaskets?

Thank you

[99yam40]

I never heard of someone doubling up head gaskets.

could the heads been shaved and they wanted to put some back . Shim the heads(increase combustion chamber volume /reduce compression)

[HarriesDGH]

I never heard of someone doubling up head gaskets.

could the heads been shaved and they wanted to put some back . Shim the heads(increase combustion chamber volume /reduce compression)

Thanks for the reply. Your shaved head suggestion was my initial thought. I bought the engines 2nd hand over 17 years ago, so don't have the background.