Well, to get you started, the 1.3 hp = 746 * 1.3 = 970 watts
970 watts / 24v = 40.4 amps.
Now the question is, is it 1.3hp continuous or peak.
Also, voltage tends to be linear based on rpm, but your numbers seem to show otherwise. Maybe you fried your voltmeter too. I know my 200v dc setting on one of my meters is not accurate by about 20%, which was probably caused by shorting the amp meter on a lawnmower battery.
Either way, your motor is either 50 to 100 rpm/volt, which is kind of high for wind / slow hydro. Maybe on a pressurized hydro, because I have seen people have success with higher rpm/volt wet ups.
What are the dimensions? And the weight?