I've always wondered how does one convert pounds of thrust to horsepower?? Is there an equation or method?

There is no real direct conversion from thrust to HP.

A rough estimate is to multiply the maximum amperage draw of you motor, times the voltage of your battery.  This will give you the max wattage.  Divide this number by 746.  746 Watts = One Horsepower.  As an example, if the maximum amp draw of your TM is, say 40 Amps and you have a 12 Volt battery, then your maximum wattage would be 480 Watts.  Divide that number by 746 and you get 0.6 HP.

I spent some time trying to figure this out a few years ago when researching the cost difference between a small HP outboard and a high lb TM for a small jon boat and found no real answer. Best guess I have after all I read is an outboard is measured in HP at the propshaft and a TM is measured in lbs of thrust with the supplied prop. They're two different figures so there's no real way to compare them. Even if you COULD come up with, say, 3hp of TM (measured at the propshaft) you couldn't compare it to a 3hp outboard because the props are designed for two different purposes - the TM for quick accel and power and the outboard with a MUCH greater pitch for speed. Then there's still no telling which one might push your boat faster.

A 24 volt trolling motor would have to be using about 31 amps to equal 1 HP.  The pound thrust rating for that trolling motor is irrelevant in that regard.