Overheating of DF 40 2005

[Gapper]

Diagnosis show Overheat Gradiant 50 times.No Failure during test on anything else.The tech guy suggested I take it out on water again and check temp at sensor with Thermometer
If temp is good he said it would be the fault of the check system guages.Can this be so?If temp is high under load I,am in trouble ,possible cracked head on exhaust side of motor.
Is this a viable repair as this guy wasn,t interested.

[Pgoss8]

Might sound like an odd question but I just dealt with something very similar to yours do you have a transducer mounted on the stern of the boat?

[Gapper]

OVERHEAT Temp at sensor 75oC I,am out of luck.

[Gapper]

YES does have transducer. NO longer a sensor etc problem, its doing its job.The motor has only 350 hours on it and well looked after.Last hope might be to get to pressure valve and check.
Motor runs like a dream just gets hot and goes into limp mode.After four years of this happening it keeps running ,you think if it were a cracked whatever it would have imploded????

[Moonlighter]

The reason, I believe, for the transducer question, is because it introduces the possibility of turbulence at higher speeds affecting water flow to the motor and thus impacting on cooling.

Anything that disrupts a smooth water flow to the leg can affect cooling performance - including transducer placement, how high the engine is set on the transom tec.

I made inquiries from my Brisbane Suzuki sources, who recommended Northern Beaches Suzuki as knowledgeable in the Sydney area on the earlier models including the Johnzuki’s.

Have you actually replaced the water pump including impeller AND the stainless housing it fits into? If not that should be done.

[Gapper]

Great Thanks for that,What about a below average Propeller?Might give NBSuzuki a call.Great help, I just cant understand why such a reliable little motor is causing a niggling problem

[Pgoss8]

Exactly, moonlighter. I had an overheat problem, replaced everything I could to no avail. Boat mechanic looked at it for another issue and casually asked if I was having overheat issues. I said I was and he told me to move my transducer out. Moved it over 8" and haven't had any issues since. It was causing turbulence at the water intake and not letting the motor cool sufficiently.

[redlowrey]

Diagnosis show Overheat Gradiant 50 times.No Failure during test on anything else.The tech guy suggested I take it out on water again and check temp at sensor with Thermometer
If temp is good he said it would be the fault of the check system guages.Can this be so?If temp is high under load I,am in trouble ,possible cracked head on exhaust side of motor.
Is this a viable repair as this guy wasn,t interested.

''''''''''I thought you said that this guy was going to fix your problem, he has told you what you already know, I could get my eleven year old grand daughter to hook up a lap top on an sds port and read digital information from it, but as far as anything else she would not have a clue. You said in your first post you had a temperature of 60c that should not have made the alarm to come on, your computer would not have a clue how hot or cold it is it uses algorithms, it only knows voltage, resistance, and grounds.

[Gapper]

Yeah mate your Grand daughter may be able to do that,In Hindsight I would have loved to give her my $300 bucks.This is a steep learning curve for me and I appreciate every ones help.
The easy way out of this would be to sell the boat to some poor bloke before I fix it .But thats not me.

[Moonlighter]

It might be useful to know what make and model boat this motor on, and to take some photos at various angles of the motor and transom area close by the engine so the leg and motor an dtransducer are able to be observed.

Post them here so we can see. Not hard to do.

I am getting suspicious that there might be something causing disturbed water flow to the engine....

That, or there could be internal buildup of calcium and salt deposits that are restricting water flow and circulation in the motor. Im not familiar with this particular motor but I guess it has internal anodes? If so, Pull them out and see what the water passages look like where they fit. If theres a significant build up, a vinegar flush may help, - search this forum you will find info on that.

Or you could go back and run the tests as suggested by Red, with his guidance, to find out if what you have is just a dodgy temp sensor causing false alarms.

[Gapper]

YES defiantly overheating,Replaced anodes recently,. water passages good.Removed Hydrofoil and ordered new Propeller as this is due anyway.
The transducer and Hydrofoil were on the boat when first got it five years ago ran fine then,but will remove to test. Another test run this weekend.

[simogoes]

Hi Gapoer, did you ever solve the issue? I have the same problem!

[Pbodsw]

I used to have a 2006 DF50 and fixed my overheat gradient alarm by switching the exhaust thermister with the head thermister. They have the same part number.

To diagnose the issue I measured the resistance of each sensor in a cup of known water temperature at 10°C intervals. Both were broadly comparable and within spec at 25°C as stated in the workshop manual, but above 50° the exhaust sensor was reading much less resistance. The ECM would interpret that as if it were reading a higher temperature more quickly. The temp curve of the thermister wouldn't match the expected resistance curve programmed into the ECM. Rather than spend money, I just swopped the iffy sensor over to the head. Problem solved! Hope it works for you.