I have read different things about the disabling of the ship.

1) In Ha’aretz an IDF General said they had decided against it because the largest ship (only the largest) was too large. It would have taken too long to tow to Israel, and risked a humanitarian crisis. Take that for what you will.

2) Other commentators have said the specific type of ship likely didn’t have propellers/rudders/that sort of thing, but instead would have had some sort “water jets” that cannot be disabled from the outside.

I know nothing about ships, so I cannot say which, if either, may be likely