well, for starters, "Sears" Die hard was probably a Minn Kota made for them....
that might give you a lead on this...
nowadays, Trolling motors usually list "pounds thrust" instead of horsepower....
a general rule of thumb is that 75 pounds of thrust equals one horsepower....
now: when Trolling motors start getting into THAT area of thrust, they are often 24 VOLT systems, which means it uses TWO batteries to run it...
do you know if your TM is 24 or 12 volts????
if it is 12 volts, the "horsepower' rating might be a bit exagerrated....