Erratic Temp Issue

[Grumpy]

I have an 07 Launch SSV that is showing temperature issues. I have checked all the usual parts, Raw Water Pump, Circulation Pump, Thermostat and replaced the Temp Sensors. Even on a cold engine before start the temp can read over 180 degree and fluctuate up and down. Last weekend I put a heat gun on the motor and at no stage could I find any part of the motor indicating anywhere near the same temps as the dash displayed. Any hints on what to check next would be appreciated.

[CornRickey]

My gauge would jump all over the place even after replacing it and the sending unit. I found a bad connection in the main harness. Mine has a large round connector where the chassi harness plugs into the engine harness under the 40 amp red breaker above the tranni. It looks like a 6 round plug for trailer lights. The temp contact was corroded.

[Grumpy]

Thanks for the feedback, I had look at all terminals and hit with compressed air as well. All looks ok but unfortunately the issue is still there. Cold engine temp is starts at 70 deg c. And can fluctuate up to 90 without starting the motor. Start the motor and it be at 80 and jump to 120 and back down to 90 in the blink of an eye.

[CornRickey]

It's electrical. The sending unit is on the pulley end of the block. Passengers side under the thermostat housing. It has a single light brown wire going to it from the drives, around the front. The sending unit on the top, next to the thermostat housing is for the computer. You should be able to ground the gauge sending unit and the gauge should peg. All of this is assume that your set up its the same as mine. I'd also check the connections to the gauge itself.

[cadunkle]

Clean and reseat connection at the temp sensor. See if any change. Also check with your IR temp gun at temp sensor as well as thermostat housing. If temps are not close, as you seem to have indicated, then the sensor is bad or you've got a wiring issue. Not sure what ohms they should read at certain temps but maybe someone else knows? If in doubt replace the sensor. Typically full 12v will peg the gauge hot and more resistance with lower temps.

[Grumpy]

Clean and reseat connection at the temp sensor. See if any change. Also check with your IR temp gun at temp sensor as well as thermostat housing. If temps are not close, as you seem to have indicated, then the sensor is bad or you've got a wiring issue. Not sure what ohms they should read at certain temps but maybe someone else knows? If in doubt replace the sensor. Typically full 12v will peg the gauge hot and more resistance with lower temps.

Thanks for the feedback, have tried all your suggestions, no relief yet. I am hoping it is not a faulty ECM at this stage. Taking to an indmar dealer today will post an out come for everyone

[Grumpy]

It's electrical. The sending unit is on the pulley end of the block. Passengers side under the thermostat housing. It has a single light brown wire going to it from the drives, around the front. The sending unit on the top, next to the thermostat housing is for the computer. You should be able to ground the gauge sending unit and the gauge should peg. All of this is assume that your set up its the same as mine. I'd also check the connections to the gauge itself.

Thanks for the additional feedback, I have replaced both thermo sensors on the boat already which did not help and checked cabling to best of my ability. Am taking to an indmar dealer today soo will see what happens from here.


Fault found to be the ECM, tried a new one and temp readings all become normal

[vvfdfirefighter]

It's electrical. The sending unit is on the pulley end of the block. Passengers side under the thermostat housing. It has a single light brown wire going to it from the drives, around the front. The sending unit on the top, next to the thermostat housing is for the computer. You should be able to ground the gauge sending unit and the gauge should peg. All of this is assume that your set up its the same as mine. I'd also check the connections to the gauge itself.

Does anyone know what then tan wire with a black tracer is for that is beside the tan temp wire..mine is just dead ended

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