I don't know too much about boats, but waterproofing the esc wouldnt be a bad idea.
They say a good mechanic only needs 2 tools - WD40 & Duct tape. If it moves, and its not supposed to, duct tape. If it doesn't move, and its supposed to, WD40.
Head over to offshoreelectrics.com and join the forums...best FE boat forum on the net. FYI, the 2000kv is probably your best choice of those motors. The stock motor in the newer SV27R is 1800kv and is a 36/56 6 pole motor.