I was told that the advertised amp hours on a lithium battery was a bit of a stretch and that the batteries would not deliver what they were rated for. So this called for a test. My son found a testing strategy and I employed it on the batteries in the new trolling motor battery box.
I used a 75 watt light bulb plugged into a small inverter with a clock radio plugged into the same circuit. The batteries started at 13.4 amps and ran the inverter until they registered 10.9 amps. That took about 19 hours. I tested the draw at about 2.5 amps.
The three lithium batteries in the box are rated at 20 amp hours each. If I was drawing a full 60 amp hours at 2.5 amps it should have taken about 24 hours of power. I must assume that some power is lost in the wiring too. So I got 47.5 amp hours from my battery box. That is about 80% of the rated power. I need to recharge the batteries to completely full and test again. It appears they would still run the 40 amp trolling motor for at least an hour out on the water.