[Jimbuna]

Merchants were not designed or built for ramming (unlike icebreakers) but the sheer mass of a vessel when compared to that of a U-boat is huge.

Both vessels would receive an element of damage (escorts have been known to be totally disabled after such an action) but I'm in noe doubt the U-boat would come of far worse.

Remember, once the pressure hull of a U-boat is torn/holed, it is no longer capable of submerging.