I do not know your time and experience, but if you have to ask this question, you certainly should not be doing it.
Even if you were, you certaily should not be doing it at anything near full power.
I learned to fly in Portland Oregon where on winter days the ceiling was 3000, drizzle and haze. Even in a 152 or 172 where the speeds are slowerI never felt comfortable for even short distances, let alone 100nm, 1500 above the ground and 1500 below the clouds. Conditions can change quickly leaving you no out. The terrain elevation certainly will change over 100nm, and there is too many risks of cell twos, hills, being in IMC when not rated (which has a 20 sec average time before disorientation). I assume you are doing this because you are not IFR rated. Additionally, if there is this kind of weather, you may be in a place like the Pacific NW where there can be risks of icing in the clouds as well. At Mooney speeds, turn radius is larger leading me to think you do not have a good enough sense of maneuverability. Think of mountain flying in a canyon. You can just as easily get unexpectedly cornered in the scenario you describe. My 2 cents is - DON'T DO IT.