Calling AQ Series experts

Situation, mid season my engine was apparently over heating. At idle 200 and on plane 225 ish. This was according to the temp gauge. Replaced temp gauge with brand new and still get the same reading. I have replaced this year ; impeller, thermostat, ECT sensor, water neck and gasket along with the water tube from the neck to the transom, and have had the heat exchanger rebuilt and tested. I can shoot anywhere on the engine with an IR Gun and get 145-155 F. T-stat housing 155-160 F. Exhaust manifold is cooling properly, and heat exchanger is working properly. Any idea WTF? The mechanic i work with and i are at a loss on this one. Need help to figure out if it is over heating or if this is some sort of anomaly. Oh yeah i can stick a thermometer into the coolant resovoir and get 160 ish on the coolant it self.

Engine is aq125a

Re: Calling AQ Series experts

Check for resistance in the wiring and bad grounds. The temp gauge uses resistance to measure temperature, provided there's no ground problems or resistance in the wiring. If there is one of those issues, the gauge will pick it up and give you an inaccurate reading.

Re: Calling AQ Series experts

The wiring harness/connectors can get corrosion inside them.
WD or any silicone spray.

The 125's heat exchanger can be blocked and yet looks like it's new?
Take the bellows off the end of the manifold and check for blockage.
These manifold can look brand new and be crud filled.
Had a guy call and ask about his 131 overheating.
I told him to remove the bellows and check there.
He call back and said he's found his problem.
He tried to undo a couple of bolts and actually stuck a finger through the side of the manifold.
The paint was the only thing holding it to together?

Re: Calling AQ Series experts

At 220 F,your head gasket will be gone by now.
I agree with 500dollar744ti ,my self using IR gun to confirm engine components temperature.
Try to use your temp. gauge ,and make temporary wiring to confirm problem in main wiring.
You will need only gauge,positive from battery,ground,and signal from temp. sensor.

Re: Calling AQ Series experts

You are saying that you replaced the gauge?
Did this include the temperature sensor? That is where I would look for now.
Could be that the sensor is just bad. I had a bad sensor but it failed so it did not read at all (always cold).

Re: Calling AQ Series experts

I did troubleshoot problems like this before.
You can use your console gauge and original sensor,what you need to do run separate short wires (remove gauge from console) from gauge too sensor,to eliminate your possible wiring fault.
This way you will safe a lot of cash if problem is (most possible)in the wiring it self.

Re: Calling AQ Series experts

i used a bunch of jumper wires yesterday to eliminate the wiring harness and used 2 different gauges and still got the same reading. Used a thermocouple on my DVOM in the expansion tank and it read 161F. Sounds like i got a defective ect sensor so im going to try swapping it out for another and see what happens.