Back in the mid-50s I built free run model runabouts for this type of electric motor. If one of the neighborhood guys would purchase a motor, I would build them a boat. We would hold races across the local wading pool during summer vacation. Seems like we used the small 9 volt battery for power.
The old adage, "What goes around, comes around" applies to my electric model outboard endeavors. I'm now building electric powered "Kneeler" hydroplanes for local model boaters. We are conducting races at District 8 events using a 30 second clock and running 6 laps on 1/2 of the course.