Are you sure they are just switches with inline fuses?
They ought to be circuit breakers that trip at 10 or 20 amps depending on the cct. The rating of the cct breaker is determined by the size of the wiring for that cct.
Be very careful about replacing them if you are not sure. That’s how electrical fires start and you don’t want that on a boat.
The membership association for owners of Dufour Yachts