After finishing a refit and repainting of my John Gardner Pram I have finally been able to try it with a Torqeedo Travel 1003 motor. I was very pleased with the performance!
You can find details on the build of the pram at the link above. For comparisons sake with other prams of similar style, here are the details of the boat and performance:
Max speed with 1 person (175lbs): 9 km/hr
Max speed with 3 people and gear (~500lbs): 7.5 km/hr