It would take a great weight reduction in your current hull. Weight is a great killer of top speed in an electric boat (if you can call a rigger a boat!). True, fast electrics are all about power/weight. Is your boat 8lbs rtr, or is the hull alone 8lbs? If your hull is that heavy, if it were me I wouldn't put it in use for electric power, pick up another engine, it'll be quite a bit cheaper.

If you can get the hull/hardware down to around 6 pounds, then a Lehner 2080 might be a good choice, but you'll probably change your mind once your price out the motor and appropriate controller, and the 30+ cells that will be required to run it.... As is, maybe a Lehner 3060 will do.

If you really want a good, fast electric rigger that won't be as costly (not nearly) look into a Climate Blizzard. You can use a much smaller motor and it only requires 6-8 cells, and a controller that costs less than half of what the BIG motor will require.