Is (was) there only one capacitor in the system? Seems like a 4-brush motor might have at least one more. If so, maybe you can carefully lift one leg off and measure it?
I would surmise that it is non-essential, but I would not suggest operating the thruster without it, just in case. I'm sure Sleipner will advise the correct capacity soon enough.
Tahiti ! Lucky you 😀
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