2000 dt225 momentary temp light

[superheat216]

I am running a pair of low time dt225 on a boat I recently purchased each with a different issue that is annoying but do not ground a fishing trip. I will post each issue separately. The engine for this thread has new water pump and shows good water stream at idle (800rpm) but after start temp light and alarm present about every 15sec and last for approx. 1sec with a corresponding momentary increase in rpm. After fully warmed up occurs less frequently and not at all above 2000rpm. I have put about 20hrs on motors and symptoms have not changed. The boat was stored and not operated for about 3 years before I bought it

[seaox230c]

The sensors are located directly on top of the cylinder heads ...one is a 2 wire and one is a three wire. disconnect one, or just pull it out of the head , it is a dry unit held in by one screw and see which one is causing the fault. Change out that associated thermostat...if still bad change the sensor

[superheat216]

2000 dt225 temp light

pulled each temp sensor out of the head one at a time to no avail, do they actually need to be unplugged. Both banks feel to be same temp after warm up, can hold hand on them for long time.

[seaox230c]

If they are both out and you still have an overtemp then the sensors must be bad. I will see if anything else will trip the overheat . Disconnect each one until your fault stops

[superheat216]

Disconnected temp sensors individually and still had prob, is there a water flow sensor in this engine as it only does it at low rpm. In an effort to refine symptoms...frequent temp light below 1500 rpm, as soon as temp light comes on warning horn sounds and acts like ignition was turned off then back on, self resolves within 1-2 secs. Also noticed an occasional check engine light without horn and without engine irregularities. I am beginning to think it could be the ECM, since I have two identical motors I will trade ignition modules between the two and see what happens. Motors are the same except for counter rotation on one, would that make a difference?

[Solarman]

Counter rotation should not matter.
If still doing same thing after trying the ecm swap, get a digital laser temp gun, and check different areas of powerhead while running before buying new sensors. And check all sensor wires for possible damage, or dirty connectors.

Good luck. Post back when able to let us know.

[superheat216]

Success on the muff, moved ignition module from other engine and no temp light so ordered another module. Noticed difference in cylinder head temps using a laser gun, stbd bank warmed to 140 quickly then increased to 170 before beginning to drop, port bank remained at 108 to 130. New thermostat on the way.

[Solarman]

That could mean your ecm is working fine, but the thermostat is not. Did you check the Temps on your other motor, both banks?

Let us know.

[superheat216]

Ran other engine with ignition module from engine with intermittent temp light and did not encounter same prob. Engine ran fine and warmed well, stb bank in 140's and port in 130's with bottom cylinders running 10 degrees cooler. The problem seems to have gone away, I wonder if its the old unplug it and plug it back in fix?