I don't agree, Kyle.

The crest of Macdonald of Clanranald is -

A triple-towered castle Argent masoned Sable, and issuing from the centre tower a dexter arm in armour embowed grasping a sword all Proper.

And the motto -

MY HOPE IS CONSTANT IN THEE

There are too many differences for this to be the same or even a variation.

Regards

Chas