Overheating of DF 40 2005

[Gapper]

Can anyone help,Warning buzzer goes off and engine goes to limp mode.This happens sporadically but is happening more often.
Impeller, Thermostat,Sensors tested and all good.Pisser seems ok but lately stopped and then started again.Next step,Water pressure valve
located under oil pan thus removal of mid section.Any thoughts please

[Moonlighter]

How did you test the impeller? How old is it?

[Gapper]

Hi Moonlighter,New to this forum ,good to here from someone.This problem has been off and on for several years even with new impellers installed and water streaming from telltale.
But recently happens all the time on a short trip. Thinking that if I disconnect the return hose at thermostat and slowly pour water down hose the water pressure valve should be closed and not let water
thru as it does.If valve is open I would imagine the water pressure in the motor is not enough.The temp at motor near temp sensor is 60 oC when buzzer goes off can re start go another 10 min and goes off again.
The motor otherwise runs fine ,Never had any other trouble it Purrs like a Cat and has low hours.Thanks Gapper

[Moonlighter]

Are you using an IR sensor to check the actual temp @ 60C when the alarm goes off?

If so, 60C is not hot, theres a possibility that the temp sensor itself is faulty and the engine is actually not getting hot. Are there any other indications of overheating other than the alarm and associated safe mode?

Have you checked the wires going to the sensor to check for corrosion etc?

I think this is the part - costs about $48.

i dont know the specs, maybe someone will chime in with specs so you can measure resistance??

https://www.boats.net/product/suzuki...e8ca4d76f43dd4

[Gapper]

Thanks for that,Have checked both Temp sensor on head and Temp sensor on outlet side manifold as per Suzuki service manual.
Both are within resistance range at Three different Temperatures.Used thermometer from multi meter to test temp on head.
My problem is most mechanics in Sydney charge like a wounded Bull!

[redlowrey]

Something does not add up here, 60 degree's is operating temp, for the over temp and alarm to go off there has to be less then 200mv on your temp sensor signal line or your exhaust at the ecu. Your ecu will send five volts down the signal line through the sensor and back to the ecu to sensor ground on all three, iat, exhaust temp, and engine temp. In Sydney at the moment the ambient air temp would be around 16deg c so with the key on engine off you should be seeing around 2.8 volts or a little more on all three sensors.
As the engine warms up you should see the voltage on the temp sensor and the exhaust temp sensor dropping to around one volt or just under at operating temp, the iat sensor voltage will be around 2 volts or a bit more.
You do these simple tests and come back on the forum with the voltages you get, and I will tell you where to go next. You can check these voltages at the sensors, but to do it correctly you should be checking them at the ecu.

[Gapper]

Thanks for all help,This has now become to big an issue for my skills.Hope I can find someone with the knowledge you guys have.So far the mechanics I talk to want to dismantle the motor without proper diagnosis.I will see if I can get someone to do the above test,I do not mind paying good money to get this fixed but hard getting right advice.Thanks again

[artdf175]

So you have the Suzuki repair manual?
there are only a handful of errors that sound the alarm and cause the engine to go into the limp mode
If you tested the sensors you should be able to do what Red has mentioned

Arr

[catacom225]

Like Art Suggests get yourself a workshop manual and things will look a lot clearer , about $20 on Ebay

[Gapper]

Come over here and set up a Marine Mechanic Service and make a fortune.Obviously an under supply of Mechanics who Know what there doing in Sydney and want to charge just to book a service.
You Guys are so kind and knowledgeable

[redlowrey]

Thanks for all help,This has now become to big an issue for my skills.Hope I can find someone with the knowledge you guys have.So far the mechanics I talk to want to dismantle the motor without proper diagnosis.I will see if I can get someone to do the above test,I do not mind paying good money to get this fixed but hard getting right advice.Thanks again

'''''''''''Mate if you know how to use a digital multimeter you will be able to do this, as the others have said you need a manual with a wiring schematic, less than 20$ on ebay, if you cant go to an auto electrician not a mechanic.
You will be able to do this part easy, don't disconnect anything, get a thin sowing needle so you can slide it down the side of the connector get your multimeter on dc volts connect the black to ground, red to the needle and check the voltage of each sensor with the key on, there should be a voltage on one side and nothing on the other.

Usually the sensor ground wire will be black and white, note the voltages and right them down, as I said in my first post this is not the correct way to check the system but it will give me a bit of an idea of what is going on. I am a 1000klm to the south of you in vic. Make sure you test the meter first on the battery pos to make sure it is reading right.

[Gapper]

Ok ,Starting to get it.Have got the Manual and circuit voltage tables etc.Tested the IAT, Exhaust temp, Engine temp wires leading to sensors by disconnecting the sensor and using multimeter all three were about 2.75 volts with ignition on.I can see why i need to do the warm up engine test thru the ecu as the wires need to be connected to sensors to test voltage drop and test sensors.. Confession to make my motor is a Johnson branded motor so everything is the same wire colours from sensors etc but when you get to the diagnostic 12 pin mine is different to the manual and i cant determine which sensor wire goes to the correct pin.Johnson dont seem to have there own manual .At least I know a bit more before getting outside help

[redlowrey]

In thirty years of trouble shooting fuel injection problems, I have never seen a 2.75 volts reference voltage, checking the voltage on those three sensors while disconnected should have an open circuit voltage of five volts. That voltage should be closer to the voltage with the plugs connected.

[Gapper]

Thanks guys.Ive found a bloke who is coming Friday to have a look at my outboard.He guarantees me he will fix the problem.Will let you know the outcome.
Thanks again all,I have learnt alot

[Gapper]

PS the readings were 4.75w not 2,75w as I mentioned in previous post.Sorry to set off alarm bells