The other day I had the water from the kitchen sink running hot and noticed that it was scalding. I measured it at 150 degrees.

I looked at the Weil McLain indirect HW Heater we have and the gauge was right in the middle as it always was. That's been somewhere around 120 degrees, I think.

If I turn the gauge up and down, I do hear the "click" of it calling for and not calling for heat. At the moment I have it turned 1/4 of the way and I'm not getting water nearly as hot as before, but the temperature is really fluctuating. For a few days now, I've been checking and I've gotten readings of 116, 125 and just now about 137, all with the dial set in the same position.

Is this an aquastat problem on the HW Heater or could it be something else?

I have a Weil McLain oil boiler paired with the HW Heater.

Any ideas?