I found some specks to make evaluations.  It weighs 628grams and will put out 5 watts if you pull it through the water at 1.2 meters per second.  I don’t think in grams and meters per second. So 1.2 meters per second is about 2.7 miles per hour.  You can paddle that speed if you are not dragging an anchor. 628 grams is about 1.4 pounds. My fish detector requires about 2.8 Watts to operate.  The output voltage out of it is for charging cell phones so you will need a voltage converter (if you can find one) and that will weigh .5 to 1 pound and will only be about 90 percent efficient the power will be stored in the attached battery which will be about 95% efficient and go into the fish detector battery which will be about 95% efficient so you will get to use about 80% of the power generated in your fish detector. So 80% of 5 watts is 4 watts.  So one hour of paddling will get you about 1.4 hours of fishing time. That is a rough estimate but it gives you a estimate.  I just put together some battery packs for W13 which if wired differently would run my fish detector for 24 hours and they weigh 1.9 pounds.  Neat little gadget but I don’t want one.