We ran one of these contactors in our full size electric hydro. The speed control was rated at 2000 amps, but we didn't draw over 1000 amps in our runs. Fortunately it was donated and we didn't ask the cost. Tecknowledgey carries many smaller contactors and switches.
Not to my knowledge Gilbert. The higher current contactors are quite heavy and large and would only fit in the really large boats.
Ideally you also need a soft-start circuit to reduce the arcing in the contactor when it closes and instantly charges the caps on the ESC.
I have welded these contactors shut in HEV's when the soft start was accidentally not used.