My overheating problem. Help?

[DrivingZiggy]

Okay, so when I was a n00b I got stuck in the mud and overheated my ski. Big-ass repair bill and three years later, I still get an overheating code along with a derate into limp mode.

Yesterday I changed out the ECU to see if that was the problem--I have two identical Wave Runners. That was not the problem. Today I removed the thermostat and dropped it in some boiling water. Works as designed. I have replaced the thermosensor assembly part number 6AA-87590-00-00 a couple of times and it has not helped. So I just found on the diagram that the engine also has a thermo switch assembly part number 6CR-82560-00-00. Funds are low right now, so I don't want to buy a $82 part unless I really need to.

Is there any way to test this switch to see if it's working?

Any other ideas about what might be causing this? The piss is strong so I know the water is going through it.

[K447]

... Today I removed the thermostat and dropped it in some boiling water. ...

That is not an accurate method for testing a thermostat.

Put the thermostat in cool or warm water, alongside a thermometer. Then slowly raise the water temperature while watching the thermostat.

When you visibly see the thermostat valve begin to open, record the observed water temperature.

Boiling water certainly should trigger the thermostat to open rapidly, but the engine does not operate at that temperature. That said, I am not sure what the correct thermostat open temperature is

[DrivingZiggy]

That is not an accurate method for testing a thermostat.

Put the thermostat in cool or warm water, alongside a thermometer. Then slowly raise the water temperature while watching the thermostat.

When you visibly see the thermostat valve begin to open, record the observed water temperature.

Boiling water certainly should trigger the thermostat to open rapidly, but the engine does not operate at that temperature. That said, I am not sure what the correct thermostat open temperature is

D'oh! That's pretty much common sense. Of which I sometimes lack.

[K447]

so the engine temp sensor threads into a blind hole, meaning water doesn't actually pass by and touch the sensor itself. another inherent problem is where the sensor sits in the block itself.

if you filled the engine full of mud (sounds like you did) there is a good possibility that mud/muck has piled up in that location not allowing water to flow by and gives you an even worse (higher) temp even though the engine itself may not be overheating.

How to clean in that area?

[DrivingZiggy]

engine temp sensor

Would that be the temperature "switch?" That's the only thing I've found except for the sensor in the exhaust. And it looks like it might be in the head?

[TimeBandit]

Referencing the 2009-2012 service manual and wire charts, & I'm seeing 3 total temp sensors/switches:

Thermo sensor (exhaust) :
It's on the exhaust manifold, port side aft. Electrically, Black/Orange wire appears to be voltage supply, while the Black/Blue wire goes to pin 13 ECM. It seems this is more or less a thermistor (resistor) device which the ECM reads the active resistance. It seem you could bench-test this device by placing it into controlled hot water and taking ohms measurements. Next to freezing, resistance should be 24K-37K ohms. At boiling, 212F, 0.8K – 1.2K ohms.

Thermoswitch (engine) :
On the engine block stbd fwd. Electrically, this appears to be a switch that closes upon high temp. Black/Orange wire appears to be voltage supply, while the Pink wire goes to pin 64 ECM.
Again, a bench-test in controlled hot water can be done. It either has continuity, or it doesn’t between the two pins. 201F seems to be the magic temp. Above = closed, below = open (give or take 12 degrees).

Engine Temperature sensor (engine) :
It's also on the engine block, stbd aft. Electrically, this is another resistor-type sensor. Black/Orange wire appears to be voltage supply, while the Black/Yellow wire goes to pin 23 ECM. Same bench-test as the exhaust sensor, but different set-point values. At room-temp (68F) you should see 54K-69K ohms. At boiling point (212F) it should only have 3.1K-3.5K ohms.

Since your funds are limited, the 3 above tests are all FREE given you have both time & an ohm-meter. Least you'll know for sure which sensor is causing it. AND "if" your sensors pass these tests, then you’ll want to be looking for mechanical blockage, etc. . . check your pump intake screen, lines, and yes perhaps some mud/gunk trapped inside the engine waterjacket.

[fx160]

I would be disconnecting hoses and flushing out the mud
As I would suspect there is mud blocking water flow somewhere

[DrivingZiggy]

Referencing the 2009-2012 service manual and wire charts, & I'm seeing 3 total temp sensors/switches:

Thermo sensor (exhaust) :
It's on the exhaust manifold, port side aft. Electrically, Black/Orange wire appears to be voltage supply, while the Black/Blue wire goes to pin 13 ECM. It seems this is more or less a thermistor (resistor) device which the ECM reads the active resistance. It seem you could bench-test this device by placing it into controlled hot water and taking ohms measurements. Next to freezing, resistance should be 24K-37K ohms. At boiling, 212F, 0.8K – 1.2K ohms.

Thermoswitch (engine) :
On the engine block stbd fwd. Electrically, this appears to be a switch that closes upon high temp. Black/Orange wire appears to be voltage supply, while the Pink wire goes to pin 64 ECM.
Again, a bench-test in controlled hot water can be done. It either has continuity, or it doesn’t between the two pins. 201F seems to be the magic temp. Above = closed, below = open (give or take 12 degrees).

Engine Temperature sensor (engine) :
It's also on the engine block, stbd aft. Electrically, this is another resistor-type sensor. Black/Orange wire appears to be voltage supply, while the Black/Yellow wire goes to pin 23 ECM. Same bench-test as the exhaust sensor, but different set-point values. At room-temp (68F) you should see 54K-69K ohms. At boiling point (212F) it should only have 3.1K-3.5K ohms.

Since your funds are limited, the 3 above tests are all FREE given you have both time & an ohm-meter. Least you'll know for sure which sensor is causing it. AND "if" your sensors pass these tests, then you’ll want to be looking for mechanical blockage, etc. . . check your pump intake screen, lines, and yes perhaps some mud/gunk trapped inside the engine waterjacket.

Thanks! Somehow I missed the rear one. But it is in the diagram for $98. Shewwwwwwww! Thanks for the tutorial, I'll do that as soon as possible.

I would be disconnecting hoses and flushing out the mud
As I would suspect there is mud blocking water flow somewhere

Thanks. All hoses have actually been replaced, but I suppose that more mud could have flushed out of the engine's coolant passages and got stuck there. I'll double check.