Fast and wild temperature fluctuations, what gives?

[5:00]

I have been on travel like crazy lately and finally got to get out on the boat this weekend for some fun but...

I am getting some crazy temp ranges within seconds. I am seeing about a 25*F temp drop in about 10 seconds then it will come back up again to where it was within about 20 seconds. It seems to be pretty random but I am usually at idle at the time it happens I believe. I keep a pretty regular eye on the temp.

I don't ever remember seeing anything like this before. I replaced the impeller a couple of weeks back so it is new.

Any ideas on this, impeller, sending unit, gauge, thermostat stuck?

[gregski]

I would investigate the sending unit and wiring. Higher resistance indicates lower temperature. A loose wire (or poor ground) could easily wiggle around and make a poor connection/higher resistance which would look like a lower temperature. Likewise the sensor could be on its way out.

[ranger098]

I have been on travel like crazy lately and finally got to get out on the boat this weekend for some fun but...

I am getting some crazy temp ranges within seconds. I am seeing about a 25*F temp drop in about 10 seconds then it will come back up again to where it was within about 20 seconds. It seems to be pretty random but I am usually at idle at the time it happens I believe. I keep a pretty regular eye on the temp.

I don't ever remember seeing anything like this before. I replaced the impeller a couple of weeks back so it is new.

Any ideas on this, impeller, sending unit, gauge, thermostat stuck?

Sounds pretty normal IMO. unless it goes out of average range and it seems like shes going to overheat I wouldnt be too alarmed.

[5:00]

New sender is on the way to me and hopefully in time for the weekend.