I finally purchased an O.S. Lower unit and adapter plate and spare shaft for my TS3 hull. Now I'm looking for motor choices. From the reading I've done to date, it looks like 2000kv seems to be the way to go for 4S or 5S operation? I have the UL-1 stock motor, the Spartan stock motor and a Castle 1512-2650kv motor as possible options. Of course, going with the UL-1 motor means I'd have to find a new motor for the UL-1...or just buy another one. :)