Agreed. And even if the motor could take the load, the OP’s 25’ coil will be nowhere near enough. Think 4x that much in length and add fins/heat sink to increase thermal transfer.
25' of copper would not be nearly enough to do the whole job but it would lower the temp some, and over time it would lower the temperature relatively safely ( safe against freezing the lines ) and likely consistently unless the tub is continuously filled with mammals or in sunlight or sunlight-warmed air.