I've done a bit of research and testing on the topic of powering a dinghy with an outboard electric.
I've tried two different Torqeedo units (2.0 / 24V and 4.0 48V). Both work great, but very expensive - and you have to assume that nothing lasts forever in a salt water environment.
I also tried one of the Hangkai units. For $400, I can buy 10 for the price of one Torqeedo... My experience is that yes, it ran fine out of the box. Not as much power as the Torqeedo. VERY loud. I later learned that most of these units DO NOT have grease in the lower unit, and NEED grease added (just like any other outboard) - but the instructions don't say anything about it, and most of us assume that electric motors don't need gear grease, as most electric outboards have direct drive motors in the lower pod... Anyway, if you get a Hangkai - find a youtube video on how to add gear grease to the lower unit.
For 48V motors, I second the prior post comments on using Ebike batteries. I have used several of these and had good experiences. You do have to manage your power, and you will never get the full power out of a Torqeedo with just an Ebike battery. But it'll work.
I also tried a standard 12V trolling motor. The problem with trolling motors is the prop. The pitch of the prop simply won't push a dinghy any faster than 2-3mph. Ok if you're fishing. A bit slow, but will get you from boat to shore (if it's close).
My best compromise so far is the Newport Kayak trolling motor. It's $200 (dirt cheap), runs off a 12V lithium battery (easy to get), and will push the dinghy. It's slow. Top speed is maybe 3-4mph. You certainly will never get on plane, and you need to be thoughtful about how far you intend to go. But for a simple dingy from anchored boat to shore, it's great. We did a test run taking the dinghy to a restaurant for dinner. Motored 2 hours round trip on a single 150Ah Lithium 12V battery with the Newport motor. This was running at top speed ("5"), and averaged about 2.2 knots (~2.5mph) as per Navionics.
Bottom line, I like the Newport a LOT better than the Hangkai. Cheaper, much quieter, seems to run well. Just understand you will have to be patient.
Please feel free to contact me off-list if you have any further questions, or would like to see more data.