Yes.
Found a youtube video that shows how the valve assembly comes apart.
HEREYou will end up with a flange that stays connected to your tank, the other flange is the open side and the valve body goes in between the two flanges.
Personally, it IS the wrong valve for this application, there is zero need for a 1 1/2" drain on the fresh water tank unless you are planning to put out forest fires with it.. And boy, with the crud build up inside that valve I would hate to think about what water the previous owners put into that tank.. Man that is ugly mineral residue.
I would suggest once you have the valve out see if the flange on the tank side can be removed (IE not spun welded or glued in place) and then get a 1 1/2" to 1/2" pipe reducer and put a standard off the shelf 1/2" valve you would use for pressurized plumbing..