8148A Aquastat questions

[ToltingColtAcres]

The 8148A aquastat on my boiler apparently crapped out... relay would switch on, but the circulator pump would not energize (no power on C1/C2). I stopped at a plumbing supply house on the way home and picked up a replacement.

I have a couple of questions perhaps someone can answer.

The boiler seems to be short-cycling tonight. Kick on, run for several minutes, turn off, and then back on again in 5 minutes. It seems to be cutting off at 180 and back on again at 170, from what I can see. I've read the aquastat has a built-in temp differential of 8 degrees, but, honestly, I don't recall the boiler cycling on and off so much with the "old" aquastat -- even when it was working correctly Has the 8148A always had an 8 degree cycle point?

Can someone explain the how to properly set the temperature on the "new" aquastat. I'm unclear on what the purpose of the little lever is on the dial. The old 8148A didn't have this little lever, it was just set to 180 degrees. I set the new 8148A to 180 by putting the dial at 180 (based on the "old" setting), and it seemed to shut off at 170. So I turned it up to 190, and now it seems to shut off at 180... What's the little lever thing supposed to do?

Finally, the "old" aquastat has some odd wiring (see wiring jpeg)... runs from L3 to B on the temperature wheel housing. I did not recreate this 'jumper' on the new 8148A, I did not understand the purpose (I thought the relay clicked on when the thermostats called for heat, thus energizing 'B', and the temperature setting would determine whether or not to fire the boiler or just turn on the circulator pump... so why this jumper was there, I'm confused (boiler does not have tankless hot water). Could this be why the boiler seems to be short cycling?)

Would appreciate some education from those "in the know".