Cas. Two problems there, possibly related…
Sinking is normally due to excessive water ingress, or careless piloting.
Motors stopping GENERALLY electrical, but there again if the, say, propshaft is binding or something, then too much currrent will be taken by the motor and, if you have an Mtronics Viper , for instance, it will cut out as a safety feature.
Not so sure your problems are related. I would carry out an extended bath test first, ballasting down the boat to see if water is coming in anywhere. UNLESS you were zooming along and simply flooded the boat from excessive wash/bow wave?
Picture, we need a photo. Or at least, what sort of boat is it.. Passenger?
Ashley